AN ECOLOGICAL STUDY OF SOME OF THE CHIRONOMIDAE
INHABITING A SERIES OF SALINE LAKES
IN CENTRAL BRITISH COLUMBIA
WITH SPECIAL REFERENCE TO
CHIRONOMUS TENTANS FABRICIUS
by
Robert Alexander Cannings
BSc. Hons., University of British Columbia, 1970
A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE
in the Department of Zoology
We accept this thesis as conforming to the required standard
THE UNIVERSITY OF BRITISH COLUMBIA
May, 1973 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study.
I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.
Department of
The University of British Columbia Vancouver 8, Canada
Date ii
ABSTRACT
This thesis is concerned with a study of the
Chironomidae occuring in a saline lake series in central
British Columbia. It describes the ecological distribution of species, their abundance, phenology and interaction, with particular attention being paid to Chironomus tentans.
Emphasis is placed on the species of Chironomus that coexist in these lakes and a further analysis is made of the chromo• some inversion frequencies in C. tentans.
Of the thirty-four species represented by identifiable adults in the study, eleven species have not been previously reported in British Columbia, five are new records for Canada and seven species are new to science.
The chironomid fauna of the lake series is divided into dominant associations whose existence seems to depend on salinity and productivity levels. A Cricotopus albanus - Procladius bellus - Ablabesmyia peleensis association pre• vails in the lowest salinities (40 to 80 jumho/cm conductivity) while in conductivities between 400 and 2800 jumho/cm a Glyptotendipes barbipes - Einfeldia pagana association domin• ates. In the most saline lakes (conductivity 4100 to 12000 jumho/cm) a Calopsectra gracilenta - Cryptotendipes ariel association is characteristic.
Analysis of physical and chemical factors influencing the life cycle of C. tentans indicates that conditions associated with high levels of organic carbon promote large numbers of
larvae and greater emergence success. The results suggest
that competition between C. tentans and other Chironomus
species is reduced through spatial separation due to different preferences for salinity or related factors. Furthermore,
temporal separation among these and other abundant species
such as G. barbipes and E. pagana occurs as a result of
staggered generation times.
The inversion frequency in chromosome 1 of C. tentans is negatively correlated with organic carbon levels and posi•
tively correlated with dissolved oxygen and the abundance of
Glyptotendipes barbipes. Since the inversion frequency is
lowest in habitats where competing species are few and where
C. tentans is most successful, it is suggested that the inver•
sion governs a mechanism reducing competition.
A major contribution of this work is the revision of the
distribution of many of the chironomid species under considera•
tion. In the past, little research has been done on popula•
tions of chironomids in a saline lake series. The present
study, in attempting to fill this gap in entomological research,
shows that a species' life history and population structure
can vary radically in closely associated lakes of differing
chemical and biological constitution. IV
TABLE OF CONTENTS
Page
Title Page i
Abstract ii
Table of Contents iv
List of Tables vi
List of Figures viii
List of Plates xi
Acknowledgements xii
I INTRODUCTION 1
II THE LAKE ENVIRONMENTS 4
A. THE STUDY AREA 4
B. THE PHYSICAL AND CHEMICAL PROPERTIES OF THE LAKES 8 III SPECIES DIVERSITY AND THE CHIRONOMID COMPLEX IN THE LAKE SERIES 17 A. MATERIALS AND METHODS 17 1. Temperature Records 17 2. Biological Sampling Methods 17 a) Larval Sampling 17 b) Adult Sampling 19 3. Rearing of Specimens 23 4. Preparation and Identification of Specimens 24 5. Analysis of the Data 24 6. Storage of the Data for Further Study 24
B. RESULTS 26
1. Water Temperatures in the Lake Series 26 2. Chemical Data 30 3 The Occurrence of Species in the Lakes 30 4. Species Considered in Detail 33 5. The Chironomid Complex and the Lake Series 85
a) The Cricotopus albanus - Procladius bellus - Ablabesmyia peleensis association 85 b) The Glyptotendipes barbipes - Einfeldia pagana association 86 c) The Calopsectra gracilenta - Cryptotendipes ariel association 88
C. DISCUSSION
1. The Chironomidae and the Lake Series 91 2. Chironomus tentans and the Lake Series 102
a) Physical and Chemical Influences 102 b) Biotic Interactions 106
IV CHIRONOMUS TENTANS AND SOME BIOTIC FACTORS AFFECTING CHROMOSOME INVERSION 113 A. MATERIALS AND METHODS 113 B. RESULTS 115 C. DISCUSSION 121 r V CONCLUSION 125
Literature Cited 129
Appendix 140 vi
LIST OF TABLES
Page TABLE I Physical and chemical properties of the lakes. 10 TABLE II Average water temperature in the lake series. 27 TABLE III The distribution of chironomids in the one meter depth zone in the lakes. 31 TABLE IV The distribution of larvae unidentified to species. 32
TABLE V Summary of correlation coefficients describing the relationship between environmental factors and the amount of emergence of certain species. 76
TABLE VI The correlation between emergence histogram dispersion and environmental factors. 77 TABLE VII Summary of correlation coefficients describing relationships between environmental factors and species abundance. 78 TABLE VIII Summary of correlation coefficients describing the relationship between environmental factors and species per cent composition. 79
TABLE IX Summary of correlation coefficients describing the relationship between environmental factors and the amount of emergence. 80 TABLE X Summary of the correlation coefficients describing the relationship between environmental factors and the number of emergence peaks for various species. 81
TABLE XI Summary of correlation coefficients describing the relationship between environmental factors and the times of major emergence in several species. 82 VIX
TABLE XII Summary of correlation coefficients describing the relationship between larval abundance, numbers of emerging adults, number of emergence peaks and emergence time. 83
TABLE XIII The developmental rates of C. tentans in various lakes. 84 TABLE XIV The percentage composition of species in the lakes based on the total adult emergence, May - August, 1970. 90
TABLE XV Inversion frequencies in chromosome 1 of C. tentans. 116 TABLE XVI Summary of correlation coefficients describing the relationship between the frequency of 1 Rad and some environmental factors. 117 TABLE XVII Summary of correlation coefficients describing the relationship between the frequency of 1 Rad and the abundance of some chironomids. 118
TABLE XVIII Summary of correlation coefficients describing the relationship between the frequency of 1 Rad and the per cent composition of some chironomids, 119
TABLE XIX Summary of correlation coefficients describing the relationship between the frequency of 1 Rad and some emergence variables. 120 viii
LIST OF FIGURES
Page
FIGURE 1 The study area; Springhouse region. 5
FIGURE 2 The study area; water bodies in the Chilcotin region. 6
FIGURE 3 Details of the emergence trap. 22
FIGURE 4 Daily temperature range in some of the lakes where Chironomus tentans is abundant. 28
FIGURE 5 Cumulative day degrees measured at the mud surface at a depth of 1 meter in some of the lakes where Chironomus tentans is abundant. 29
FIGURE 6 The emergence of adults of Procladius bellus (Loew) and Procladius freemani Sublette from the one meter depth zone of several lakes. 35 FIGURE 7 The emergence of adults of Procladius dentus Roback from the one meter depth zone of several lakes. 37 FIGURE 8 The emergence of adults of Procladius clavus Roback and Ablabesmyia peleensis (Whalley) from the one meter depth zone of several lakes. 40
FIGURE 9 The emergence of adults of Cricotopus flavibasis Malloch and Cricotopus albanus Curran from the one meter depth zone of several lakes. 43
FIGURE 10 The emergence of adults of Psectrocladius barbimanus (Edwards) from the one meter depth zone of several lakes. 45 FIGURE 11 The emergence of adults of Crypto- tendipes ariel (Sublette) and Calopsectra gracilenta (Holmgren) from the one meter depth zone of several lakes. 47 ix
FIGURE 12 Larval abundance and adult emergence of Perotanypus alaskensis (Malloch) in L. Lye, Boitano L. and L. Jackson. 50
FIGURE 13 Larval abundance and adult emergence of Derotanypus alaskensis (Malloch) in Rock L., Sorenson L. and East L. 51 FIGURE 14 Larval abundance and adult emergence of Einfeldia pagana Meigen in L. Jackson, Rock L. and Westwick L. 55
FIGURE 15 Larval abundance and adult emergence of Einfeldia pagana Meigen in Near Opposite Crescent, Barkley L. and East L. 56
FIGURE 16 Larval abundance and adult emergence of Glyptotendipes barbipes (Staeger) in L. Jackson, Westwick L. and Sorenson L. 58
FIGURE 17 Larval abundance and adult emergence of Glyptotendipes barbipes (Staeger) in Rock L., Barkley L. and East L. 59
FIGURE 18 Larval abundance and adult emergence of Chironomus anthracinus Zetterstedt in Boitano L., L. Jackson and Rock L. 62
FIGURE 19 Larval abundance and adult emergence of Chironomus anthracinus Zetterstedt in Sorenson L., Barkley L. and East L. 63 FIGURE 20 Larval abundance and adult emergence of Chironomus n.sp. in Barnes L., Boitano L. and L. Jackson 66
FIGURE 21 Larval abundance and adult emergence of Chironomus n.sp. in Rock L. and Sorenson L. 67 FIGURE 22 Larval abundance and adult emergence of Chironomus n.sp. in Barkley L. and East L. 68
FIGURE 23 Larval abundance and adult emergence of Chironomus tentans Fabricius in L. Jackson, Westwick L. and Sorenson L. 74 FIGURE 24 Larval abundance and adult emergence of Chironomus tentans Fabricius in Rock L., Barkley L. and East L.
FIGURE 25 Chironomid larval biomass and index of diversity for the larval complexes at 1.0 m in the lake series FIGURE 26 Graph showing the relationship between . oxygen levels and organic carbon in the lakes.
FIGURE 27 Salinity tolerances of the identified species of the one meter depth zone in the lake series.
FIGURE 28 Examples of the spacing of emergence times of Chironomus tentans and three coexisting species.
FIGURE 29 Seasonal variation in the frequencies of inversions of chromosome 1. LIST OF PLATES
Page
PLATE 1 A Box 27 11
B Box 27; vegetation
PLATE 2 A Barkley L. 12 B Barkley L.; Myriophyllum
PLATE 3 A Near Phalarope 13 B Near Opposite Crescent
PLATE 4 A L. Greer 14 B L. Jackson
PLATE 5 A L. Lye 15 B Round-up L.
PLATE 6 A Barnes L. 16 B Barnes L.; precipitated salts
PLATE 7 The emergence trap 21 xii
ACKNOWLEDGEMENTS
It is a pleasure to express my gratitude to Professor G.G.E. Scudder who, as my research supervisor, guided me through this work. The time and energy he spent are much appreciated.
Dr. T.G. Northcote1s criticism was invaluable during the writing of the thesis. I also thank Dr. A.B. Acton for reading the manuscript. Dr. M.S. Topping, whose PhD. thesis served as the basis for the present study, is especially thanked for his enthusiasm, support and permission to use much of his unpub• lished data.
Glen Jamieson, Tony Dixon and Ken Bowler somehow put up with my innumerable questions about computer programming. Without their help the data analysis would have resembled an infinite loop, or worse, would have crashed the system.
Julian Reynolds, in between snickers, did all sorts of things to help.
I am indebted to Dr. J.E. Sublette (Eastern New Mexico University) and Dr. D.R. Oliver (Canada Agriculture, Ottawa) for their help with the determinations. Dr. A.M. Hutson (British Museum: Natural History) kindly supplied authentic specimens of Einfeldia pagana and Psectrocladius barbimanus for identification purposes.
The research was carried out while in receipt of a National Research Council of Canada Postgraduate Scholarship and was further aided through an NRC grant to Dr. Scudder. ERRATA
1. Where "Aphanozomenon" appears, read "Aphanizomenon".
2. Page 26, line 18. "31° in L. Jackson" should read "31° in Barkley L.".
3. Page 61, line 15. "univoltive" should read "univoltine".
4. Page 88, line 17. "12000 umho/cm".
5. Page 102,line 18. "not real trend" should read "no real trend".
6. Page 126, line 2. "eighteen species new to B.C., twelve species new to Canada and seven species new to science". 1
I INTRODUCTION
This thesis is an ecological study of some of the
Chironomidae inhabiting a saline lake series in the Chilcotin and Cariboo regions of British Columbia. The chironomid complex of a saline lake series has never been thoroughly examined before. Rawson and Moore (1944) and Lauer (1969) have mentioned chironomids in connection with work on saline waters, and others have recorded and studied various species in waters of differing salinities throughout the world
(Remmert, 1955; Sutcliffe, 1960; Palmen, 1962; Bayly and
Williams, 1966), but little information has been gathered on how chironomid populations differ in a series of lakes of varying salinity.
This type of study is particularly interesting since it is well known that chironomids display extensive adaptation to a wide variety of environments (Thienemann, 1954; Brundin, 1966) and are often able to thrive where many other animals cannot. The broad salinity tolerance of the Chironomidae gives them special prominence in saline habitats. This fact, in con• junction with their usual great abundance and wide diversity, makes chironomids useful organisms with which to study changes in the structure of species complexes that occur with varia• tions in physical, chemical and biological conditions.
The data obtained by Topping (1969) on this lake series in central British Columbia showed that in the dipteran 2
Chironomus tentans Fabricius there was a significant corre• lation between the frequency of larval chromosome inversion
1 Rad and the total number of other chironomids present in the habitat. Since the selective value of inversions in wild pop• ulations is not clearly understood, and as there have been few correlations of this sort, further investigation of this prob• lem is considered valuable.
Although Topping was able to show this correlation between inversion frequency and larval abundance, most emphasis was placed on the chemical composition of the environments and little attention was directed to the biotic factors involved. Thus, one of the main aims of this thesis was to ascertain the effects of some biotic factors on the abundance of Chironomus tentans and the implications of these factors on the regulation of inversion frequency.
In particular, it was considered necessary to know more about the other chironomid species that coexist with C. tentans in this lake series, their numbers and their life cycle
characteristics. Only after determining the variations in the structure of the chironomid complex throughout the lake series is it possible to place the populations of C. tentans in proper perspective and to investigate the influence of the various species on C. tentans.
Initially, attention is directed to the lake environments
themselves; their physical and chemical characteristics are
outlined. This information, in conjunction with extensive 3 data collected on larval numbers and emergence patterns, is used in an examination of the major species of the one meter depth zone. Questions such as the effect of lake environments on the distribution and phenology of these species are dis• cussed as are the possible interactions between the more domin• ant species present.
The physical and chemical data are then integrated with information on chironomids and thus a description of a number of species associations is advanced. These associations, vary• ing throughout the lake environments, form the basis for the examination of the relationship between C. tentans and the other species.
With these data at hand the potential effect of the biotic factors on the chromosome inversion frequency in C. tentans may be more closely analyzed. Correlation coefficients are calculated to determine the types of interactions that may prove important In this respect.
A particularly interesting problem that arises from the study of interspecific interactions is the apparent coexistence with C. tentans of two other very similar Chironomus species, C. anthracinus Zetterstedt and C^n.sp. (near atritibia Malloch). Attention is focussed on this congeneric interaction and com• petitive exclusion (Hardin, 1960) is discussed in this context. 4
II THE LAKE ENVIRONMENTS
A. THE STUDY AREA
The study was undertaken in the Cariboo and Chilcotin areas of central British Columbia. The fifteen water bodies examined are situated in two distinct but adjacent areas: the Springhouse area southwest of Williams Lake east of the Fraser River; and Becher's Prairie near Riske Creek on the western (Chilcotin) side of the Fraser (Figs. 1, 2). Those named as lakes can be found on maps while the others have names used for the convenience of zoologists. The water bodies include: a) Springhouse area: Sorenson Lake, Westwick Lake and Boitano Lake b) Becher's Prairie (Chilcotin Area): Barnes Lake (Box 4), Round-up Lake (Phalarope), Lake Lye (Box 20-21), Lake Jackson (Near Opposite Box 4), Lake Greer (Box 89), Rock Lake, Near Phalarope, Near Opposite Crescent, Box 17, Barkley Lake (Opposite Box 4), East Lake (Racetrack) and Box 27. FIGURE 1
The Study Area: The three lakes in the Springhouse region.
Insets : The Fraser Plateau and its location in the province of
British Columbia. 5 FIGURE 2
The Study Area: water bodies in the Chilcotin region
7
The lakes are contained in the Chilcotin and Cariboo parklands biotic areas (Munro, 1945; Munro and Cowan, 1947) at an elevation of about 1000 meters. The terrain is a rolling savanna-type upland characterized by Agropyron (bunchgrass) and stands of Populus tremuloides, Pseudotsuga menziesii and
Pinus contorta.
The climate is characterized by relatively low average annual temperatures (the means for January and July at Big o o Creek being -10.6 C and 13.3 C respectively), large fluctua• tions in seasonal and daily temperatures and low precipitation
(12.66 inches at Big Creek annually) (Scudder and Mann, 1968;
Topping, 1971). The lakes are ice covered from mid October to late April. 8
B. THE PHYSICAL AND CHEMICAL PROPERTIES OF THE LAKES
The water bodies were chosen so as to obtain as wide a
range of salinity as possible with respect to the occurrence
of chironomids. In particular, the lake series contains the
entire gamut of water chemistry tolerated by Chironomus
tentans (Topping, 1971). While salinity varied, the use of
this particular lake series kept other environmental para• meters such as physical location and climate as similar as
possible. In addition, the waters lack inlet and outlet
streams, lack fish predators and are subject to disturbance
by cattle (Scudder, 1969 A).
The lakes vary both in size and character; the larger, more saline lakes are generally dominated by NaHCO^ while in the smaller, fresher ones MgCO^ prevails. This must be con• sidered only a general trend, however, (East Lake is a rela• tively large, fresh water body with sodium as the dominant cation while Near Phalarope is a much smaller though more saline lake, dominated by the sodium ion) and the chemically prevalent ions are no doubt related to the composition of the underlying rocks rather than to the size of the water body (Cummings, 1940; Topping, 1969).
Some shorelines are relatively steep and firm while
others are very shallow and extremely soft. The latter
character seems to be associated with certain productivity or
chemical levels supporting marginal Scirpus acutus growth
(Sorenson Lake, Westwick Lake, Near Phalarope) and heavy 9
concentrations of rooted aquatics such as Myriophyllum
(Rock L., Barkley L.), Najas (Sorenson L. , Westwick L.) and
Potamogeton (Box 27) (Munro, 1941) (Plates 1-3).
From mid-June onwards algal blooms are common in most
lakes, especially filamentous greens such as Spirogyra and
Zygnema in Sorenson Lake and bluegreens such as Aphanozomenon
in Near Opposite Crescent, L. Jackson, L. Greer and East Lake
(Plate 4). In the more saline lakes emergent vegetation is
absent as are heavy algal blooms (Plates 5, 6). These lakes usually have relatively firm margins ringed with white salt
deposits (Plate 6).
The most striking change in the fauna between the low and high salinity lakes is the replacement in the higher salinities of the varied amphipod and cladoceran crustacean fauna by great numbers of copepod crustaceans.
The general physical and chemical properties of the water bodies are shown in Table I. TABLE 1
The Physical and Chemical Properties of the Lakes. Modified from Topping (1969) and Scudder (1969 A). PI CO ga n z po t-1 t-1 w po to G> W o i ro o 0 o o (u w X ro p> H ro Bro n H- c H rr !>r 01 ri a 1 7? O t-i rr 3 3 Water Body r-* o ro3 tl 1 p> Cl a ^4 ro o 01 •fl o 3 ro i 0ro1 ro 3 13 o o 3' ro 7T O c 3 0la ] 1 ron 0o n 1 •a 1 r In r* t- o
ho 1 Ln LO H* CO 4> LO t •o Nl ON CO Ln •p- Ln ON o Ln o Area (Ha) LO o Ui ON CO Lo O CTN CO - J Ul CO r o Lo Lo •^J CO ro ON o 00 LO o o 4>
1 1 o (-* O I- h-* 1 r-» t-* r- ro to to Mean Depth (m) Ln NO *-J t-* •O LO Lo r-* o •P- ~-j CO ON
r-* ON ho to LO 4> LO ho ho ro 4> Ul ON j 1 Max.Depth (m) Ul Ul M Lo LO Ln O Ul LO LO Ul ho V
S Z z •z Z KZ Z Z Z Main Cation 09 pi 09 09 09 09 p » m 09 P1 » P> P EC EC 33 EC EC a cc EC EC EC EC n o o n o n n O O O O n o n n n W o n o n o o o Main Anion o o o o o o o O O O O o o o o o o o o o o o o o LO LO Lo LO LO LO Lo Lo
Highest ho Recorded Con• ductivity umho/cm Mean Conduc•
tivity 0 umho/cm 25 C
Ln T.D.S. O mg/1
Na meq/1 •P- ui r-1 *- -o.
K
meq/1 O o ON •p- ~J *o to •p- Ca meq/1 Mg meq/1
O •P- co3 CO CO meq/1 CO ON
HCOo meq/1
o O O O O O O O r-> LO NS Ln Cl NS NS t~* LO LO ro Ln r-1 ON O •P- LO meq/1 O t-1 -P« 4> Ln •p- LO vD -vj LO h-* •^1 -0 O O
NS ro l_* NS S04 O H* CO Co 1 Ln O O O VO O O NS ON r- meq/1 o LO -P« h-' LO ro ro NS 00 00 vO LO 00 vO ro o *-J -P- Lo 00 O vO LO VO 4> -P-
•P* Ln -p- Ln LO ro ro LO Ln Ln •P* Ln Ln Ln vo LO VO vO ro 00 00 LO LO LO o LO ON °2 mg/1 r-» H* •vi CTv 00 00 00 CO 00 00 00 00 03 vO 00 VO VO VO Mean pH 4> LO ON ON CO VO 4> VO ON o vD ro CO t-* •P* •P* Ln •P- vO ro CO 4> H* r-* Ln ON •vj •P- ro Per cent CO vO 4> N> 00 ro O ro VO ro Cn ro VO •P- organic LO NS ro LO Ln vO o ro o ^4 carbon OT PLATE 1 Box 27, the freshest of the lakes. Note the extensive mat of emergent Potamogeton natans. A closeup of the vegetation in Box 27. 11 PLATE 2 A. Barkley Lake, a good example of the shallow, soft-edged type with abundant Myriophyllum. B. Barkley Lake. Myriophyllum sp. 12 PLATE 3 A. Near Phalarope. A lake in the middle range of salinity- characterized by very soft margins and abundant Scirpus acutus. B. Near Opposit Crescent. A shallow, firmer edged lake of medium salinity. 13 PLATE 4 Lake Greer, a lake with rather steep, firm margins, growths of Myriophyllum sp. and summer Aphanozomenon blooms. Lake Jackson. Steep, firm margins, small stands of Scirpus acutus and very heavy mats of Aphanozomenon. This is a lake of medium-high salinity. 14 PLATE 5 A. Lake Lye. A rise in water level has killed the Populus tremuloides stand. B. Round-up Lake. A high salinity lake with a firm, gravelly bottom. No emergent vegetation. Note precipitated salts on the shore. 15 PLATE 6 Barnes Lake. The most saline of the lakes studied. Barnes Lake. The firm margin with precipitated salts. 16 Ill SPECIES DIVERSITY AND THE CHIRONOMID COMPLEX IN THE LAKE SERIES A. MATERIALS AND METHODS 1. Temperature Records Throughout the summer temperature profiles were taken in the lakes at the mud-water interface (1 meter) with Ryan D-30 submersible temperature recorders (Ryan Instruments, Inc., Seattle). 2. Biological Sampling Methods a) Larval Sampling At weekly intervals from May 23 to August 29, 1970, duplicate larval samples were taken from each lake (except six each in Westwick Lake and Sorenson Lake) at a depth of one meter. Samples were taken from the 1 meter depth zone since this is the depth at which C. tentans is most abundant. A 15 by 15 cm Ekman dredge was used for the sampling. If the dredge was brought to the surface incompletely closed the sample was discarded. Samples were then washed and seived through a 0.56 mm mesh screen and the mud and larvae retained were stored in glass jars for further sorting. Since Jonasson (1955) states that it is the head capsule width of larval chironomids that determines whether or not they are retained by the mesh, and since Sadler (1935) reported the head capsule diameter of fourth instar C. tentans ranged 18 from 0.71 to 0.74 mm (my measurements have a mean of 0.76 mm) and that of the third instar was less than 0.40 mm (my mean measure is 0.43), only fourth instar larvae could be collected quantitatively. In this study, all the species considered in detail as larvae have head capsule widths exceeding 0.56 mm in the fourth instar. If populations of a species occurring in the different lakes can be assumed to be composed of the same relative numbers of developmental stages, then it may also be assumed that the estimates of fourth instar larvae reflect the differences in the abundance of that species in the lakes. For the purpose of evaluating generation time, only an estimate of fourth instar fluctuations along with emergence data is necessary. Quantitative analysis of bottom fauna is hindered by the labour involved in separating the insects from the sampled substrate. The usual method of extracting chironomid larvae from mud and dense plant material is by the benzene or sugar flotation technique (Salt and Hollick, 1944; Anderson, 1951; Mundie, 1957). These methods were considered impracticable for one person continuously in the field. Mundie (1957) notes that "core sampling would be made much more practicable if the larvae could be quickly and efficiently extracted from the mud and counted. Possibly only treatment of fresh cores offers prospect of this". Under the circumstances, analysis of fresh cores presented no problems; picking the easily seen red and green wriggling larvae from the collected samples was no more time consuming and just as efficient as more sophisticated 19 treatments of preserved larvae (Pask and Costa, 1971). The sorted larvae in each sample were preserved in 70 per cent ethanol. Mundie (1957) states that the top 5 cm of mud usually- con tain 95 per cent of all larvae. Inspection of the dredge samples showed that this section was almost always taken. b) Adult Sampling Pupal and adult midges were quantitatively sampled by emergence traps. Since many of the specimens trapped by this method became wet or damaged, it was necessary to preserve them in 70 per cent ethanol. The sorting of large numbers of adults and pupae under a dissecting microscope and the preparation of microscope slides for complete identification of the specimens demand such preserved material. For these reasons it was considered most useful and convenient to preserve trapped material in alcohol. This line of reasoning is followed by Roback (1971) for even netted adults, but many workers consider it important to make initial identifications using pinned specimens (Edwards, 1929) so that wing venation and some setal configurations can be more clearly characterized. Schlee (1966) and Saether (1969) raise important arguments in favour of pre• paring slide mounted adult specimens. The emergence trap samples were used to identify the chironomids inhabiting the one meter depth zone of each lake, to calculate the numbers and sequences of insects emerging 20 per unit area throughout the sampling period and to determine the life cycles of the more important species. Two traps were set out in the one meter depth zone of each lake with the exception of Sorenson and Westwick Lakes where eight traps were used. The traps were suspended under the water from a wooden cross driven into the mud. They were emptied every fourth day; care was taken not to disturb the substrate during the emptying procedure. The trap used was a modification of that designed by Hamilton (1965). Essentially it is a cone of clear acetate plastic with an eight ounce glass jar screwed into the apex. Ascending pupae enter the funnel and emerge as adults in the air space within the jar. The area of the mouth of the trap is 0.1 square meter (Figure 3; Plate 7) (Cannings, 1972). The design is similar to those used by Brundin (1949) and Jonasson (1954) except that metal screening has been replaced by clear plastic; this material makes the trap more transparent and much easier to clean. For use at one meter these traps seem ideal - they are much simpler and cheaper than the deep water models of Mundie (1956), more durable than the simpler cones used by Sublette and Dendy (1959) and less affected by wind and wave than Corbetfe (1965) floating traps. Mundie (1956, 1957) outlines the sources of error inherent in the trapping method. He states that traps may be considered to sample quantitatively if the insects do not avoid them, and PLATE 7 The emergence trap. The base of o the funnel has an area of 0.1 m . 21 FIGURE 3 Details of the emergence trap. From Cannings (1972). SETTING OF TRAP 2x2 stake ^crossbar supporting 2 traps water level lead weight mouth of trap 12" above bottom 29.5 cm DETAIL OF COLLECTING JAR supporting cords CONE/ TEMPLATE -air space 8oz. jar -water level EXPLODED small plastic VIEW OF cone TRAP bakelite ends of lid —\ cords \\~under clamp hose clamp extra strips of plastic may be wrapped around cone to prevent cracking 23 the catch may be assumed to have come from the bottom di• rectly below the trap if water currents do not cause hori• zontal movements in pupal ascents. Efforts were made to make these assumptions valid. Traps were set about a foot above the mud in order to reduce the effects of water movements and were cleaned of bacterial and algal coatings at each emptying in order to maintain maximum transparency. No doubt many of the preda- ceous organisms caught in the traps along with the midges affect the accuracy of the sample. Species of hydrachnids, zygopterans, notonectids, corixids and dytiscids were frequently trapped in the jars. 3. Rearing of Specimens By rearing adult flies from larvae all three stages of the life cycle can be identified. Complete identification is invaluable since it is frequently impossible to determine larvae past the generic level whereas male adults can usually be iden• tified to species. Fourth instar larvae were placed in individual screen- covered vials or petrie dishes containing dechlorinated water, shredded Scott tissue paper for tube construction, and small amounts of food in the form of nettle leaf powder and powdered milk. The containers were kept at room temperature in a light regime of 16 hours light, 8 hours dark. Rearing success im• proved greatly if the water was continuously aerated. 24 4. Preparation and Identification of Specimens The larvae were sorted under a dissecting microscope and were divided into groups of apparent specific and instar ranks. The volume displacement of each wet sample was taken as a rough measure of chironomid biomass. Adult samples were treated in the same manner; males, females and pupae being considered separately. Permanent mounts of representative specimens were then made on microscope slides in order that positive identification of the sorted types could be made. The method followed that of Schlee (1966) and Saether (1969). Identification followed Edwards (1929), Townes (1945), Sublette (1960, 1963, 1964, 1967, 1970) and Roback (1971). Further determinations and crosschecking were performed by Dr. D.R. Oliver (Ottawa) and Dr. J.E. Sublette (Eastern New Mexico University). The nomenclature follows Sublette and Sublette (1965) and additions and revisions in subsequent Sublette papers and Roback (1971). After the identifications were completed the collections were sorted and counted a second time. Errors due to incorrect identification of specimens and miscounting were thus minimized. 5. Analysis of the Data a) The U.B.C. TRIP (Triangular Regression Package) program (Bjerring and Seagreaves, 1972) was used to compute correlation coefficients between selected variables. The Kendall rank correlation analysis (Siegel, 1956) was employed in the few 25 correlations using ordinal measurement. These were cor• relations using emergence dispersion as a variable. b) For each lake a monthly and total average species diversity index was calculated. The function used is the entropy formula as applied to information analysis (Khinchin, 1957; Margalef, 1968). The use of this function for estimating species diversity in ecosystems has been widespread (MacArthur and MacArthur, 1961; Larkin et al, 1970; Johnson and Brinkhurst, 1971). 6. Storage of the Data for Further Study The basic data collected in this study, including computer programs and specimen.collections, have been filed for future use in the Spencer Entomology Museum, Department of Zoology, U.B.C. 26 B. RESULTS 1. Water Temperatures in the Lake Series The temperature at the mud-water interface (1 meter) in the lakes is shown in Table II and temperature profiles for five of the six C. tentans lakes under consideration are found in Figure 4. Sorenson Lake records are incomplete. All the temperature trends are similar in the lakes, the major difference among them being the variation in the daily temper• ature ranges. The difference in daily temperature fluctuation between two lakes such as East Lake and Lake Jackson and two other lakes such as Westwick Lake and Barkley Lake might be attributed to heavy Aphanozomenon (Cyanophyceae) blooms over the 1 meter depth zone in the former water bodies throughout all but the early part of the study period. Such algal mats may prevent rapid diurnal temperature fluctuations in the water. Table II shows that the mean temperature over all the lakes during the period was 17.8°C. The mean temperature of all but three of the lakes was within 1°C of this value. The highest temperature reached was 31°C in L. Jackson on July 13. The range of water temperature on this date was 15°C! (Figure 4). Cumulative day degrees for the six lakes are graphed in Figure 5. In the case of Sorenson L. the curve up to May 18 is that of Westwick L., chosen since the rest of the slope is identical in the two lakes. These plots represent mean temper• atures. From these graphs the number of day degrees that have accumulated between any two dates may be read. Since the TABLE II Average water temperatures in the lake series. Temperatures at the mud-water interface (1970). WATER BODY MAY JUNE JULY AUGUST SUMMER mean mean mean mean mean Barnes L. 12. 6 19. 2 21. 0 18. 3 19. 8 Round-up L. 12. 0 18. 9 20. 0 19. 5 17. 6 L. Lye 13., 1 19. 4 20. 1 19. 2 18. 0 Boitano L. 13. 3 18. 6 19., 8 19. 2 17. 7 L. Jackson 12., 8 1.9. 4 20., 1 19. 0 17., 8 L. Greer 12., 8 18. 6 19. 7 18. 9 17., 5 Rock L. 13., 0 18. 3 18.,5 18. 3 17.,0 Near Phalarope 10.. 5 16., 4 18., 2 17. 2 15.,6 Westwick L. 13.. 5 20., 1 21., 1 19. 3 18. 5 Sorenson L. 14., 9 18., 5 18.. 1 17. 8 17., 3 Near Op. Crescent 12., 7 19., 7 20.. 5 19. 6 18., 1 Box 17 13.. 2 19., 1 20.. 1 19. 1 17.. 9 Barkley L. 14., 9 19., 4 21., 2 18. 3 18., 4 East L. 12., 0 17.. 9 18., 9 18. 3 16., 8 Box 27 15.. 3 20., 2 20.. 4 19. 8 18.. 9 FIGURE 4 Daily temperature range in some of the lakes where Chironomus tentans is abundant. L. Jackson Rock L FIGURE 5 Cumulative day degrees measured at the mud surface at a depth of 1 meter in some of the lakes where Chironomus tentans is abundant. 29 30 generation time of a species is considered to be a function of the benthic temperatures (Mundie, 1957), species can be characterized by the number of day degrees needed to complete their development. 2. Chemical Data Physical and chemical data other than temperature are from Topping (1969) and Scudder (1969 A) (Table I). These data represent information gathered from surface waters or at a depth of 1 meter averaged over the summer sampling period. As seasonal variation in the physico-chemical properties is less pronounced than are the differences between lakes (Topping, 1969) and as the concentration data agree favorably with the ten year averages (Scudder, 1969 B; Scudder, pers. comm.), it was felt that the use of these data in subsequent phases of the work would not adversely affect the results of the investi• gation. For details on the collection and analysis of these data, and for a more comprehensive discussion of the physical and chemical properties of the lakes, see Topping (1969). 3. The Occurrence of Species in the Lakes Table III shows the distribution of species collected at a depth of 1 meter in the lakes. This should be considered only a preliminary list of the chironomid fauna of this depth zone. Adults representing 34 species, 15 genera and 3 sub• families were trapped and are listed in Figure 27 along with TABLE III The distribution of chironomids in the one meter depth zone in the lakes. Both adults and identified larvae are included. L. L. L. L. L. L. L. L. 17 27 Lye Barnes Round-up Boitano Rock Sorenson Nr.Op.Crescent Box Barkley Box L. East L. Jackson L. Greer Nr.Phalarope Westwick a • a a a e Tanypus punctipennis a • e • • « • • Derotanypus alaskensis • • e • • a a Derotanypus n.sp. • • • e a Procladius bellus • • • • Procladius nietus • • • e • • e • • Procladius freemani • • • • a • • Procladius ruris • • e • • • • • • • Procladius dentus • • • Procladius clavus • • • • Procladius sublettei • Procladius n.sp. • • Ablabesmyia peleensis • • Nanocladius n.sp. • • • • Cricotopus albanus • • • • • e • 0 • s 6 Cricotopus .flavibasis • a • • Cricotopus trifasciatus • Acricotopus nitidellus • Psectrocladius barbimanus • Psectrocladius • zetterstedti Psectrocladius n.sp; • • • • • e Chironomus anthracinus Chironomus. atrella • • Chironomus tentans • • • e Chironomus plumosus • • • • • • • • • • Chironomus n.sp. o o • o o (near atritibia) Chironomus n.sp. • • • . a a e • a • Einfeldia pagana • • • e Cryptochironomus • • psittacinus o Cryptotendipes ariel o a • • • o Endochironoraus • nigricans 1 • a • • • a e e • • Glyptotendipes barbipes 9 e o • • o Polypedilum n.sp. o Calopsectra gracilenta a e • • e e e • • « o Calopscctra holochlorus -• TABLE IV The distribution of larvae unidentified to species. L. L. L. L. L. L. L. 27 17 Op.Crescent Lye Barkley Box Box East Round-up L. Boitano Rock Sorenson L. Jackson Nr. Nr. Phalarope Barnes L. Westwick L. Greer Clinotanypus sp. 0 0 o o 0 0 0 Tanypus sp. 0 Psectrotanypus sp.A o Psectrotanypus sp.B 0 Psectrotanypus sp.C 0 0 » o e 0 e 0 © o o 0 0 0 Procladius sp.A 0 0 o 0 « 0 ' Procladius sp.B 0 Ablasbesmyia 1 o Cricotopus ? 0 0 0 0 o Chaetolabis sp.A 0 Chaetolabis sp.B o b 0 o 0 0 e 0 o o Chironomus sp.A. 0 Chironomus sp.B 0 0 0 o e 0 « 0 Chironomus sp.C 0 e 0 e 0 Chironomus sp.D 0 Chironomus sp.E o e o e 0 0 0 0 a 0 0 0 Cryptochironomus sp. O 0 e Cryptotendipe s? 0 e Cryptocladopelm asp. e 0 0 e o o • e e Endochironomus sp. « • o e 8 e o a o 0 9 o Glyptotendipe ssp.A e Glyptotendipe ssp.B • • 1 • e Parachironomus sp. e 0 0 o © o a 0 0 • o Polypedilu msp. a e e © © e • Tanytarsus sp.A e 0 0 © o • Tanytarsus sp.B 0 0 e 0 Calopsectra e " i ! o gracilenta ? r ! 1 33 their range of salinity tolerance. Twelve adults were associated with their larval forms. Other tentative species of larvae identified to genus are listed in Table IV. 4. Species Considered in Detail In order to define major differences in the chironomid communities of the lakes in this saline series, a number of the more distinctive species are considered in some detail. These are Procladius bellus, Procladius freemani, Procladius dentus, Procladius clavus, Ablabesmyia peleensis, Cricotopus flavibasis, Cricotopus albanus, Psectrocladius barbimanus, Cryptotendipes ariel, Calopsectra gracilenta, Derotanypus alaskensis, Einfeldia pagana, Glyptotendipes barbipes, Chironomus anthracinus, Chironomus n. sp. and Chironomus tentans. The first ten species will be discussed primarily with reference to chemical environmental factors and will form a basis for discussion of the lake series as a gradient of environmental conditions. The next five species will be con• sidered in a similar manner although biotic factors will also be stressed. These are the species which potentially have the greatest interaction with C. tentans. C. tentans is then described with reference to the lake series and the interactions with other species that may influence its mode of life. a) Procladius bellus This is a widespread but not abundant species. The species 34 is known only from trapped adults, since the larvae of the large Procladius genus were found to be largely inseparable. The species emerges in relatively small numbers (usually less than 10 per square meter) in all lakes it occurs in except in East L. and Box 27 where concerted emergence over a two week period amounted to 40 and 180 per square meter respectively (Figure 6). In all cases the emergence period is from late May to mid June. P. bellus appears to have only one genera• tion, although in Box 27 two peaks 24 days apart may indicate a second generation late in June. Buckley and Sublette (1963) and Sublette (1963) note that P. bellus is very widely spread in North America and tends to be a profundal dweller. Sublette (1957) found it reasonably abundant from 3 to 15 meters in Lake Texoma. Most authors state that P. bellus emerges from April or May to September or October with one generation concentrated in a spring emergence (Sublette, 1957). Judd, in three separate studies (Judd, 1953; 1957; 1961) agrees with this although in one of his emergence studies, P. bellus showed two generations, one peak coming on May 30, the second on August 13 (Judd, 1961). P. bellus is much more abundant in the fresher waters of the series (Figure 6), being less frequently found in waters above a conductivity of 800 jumho/cm (Near Opposite Crescent). Small emergences occur in Westwick, Rock, Jackson and Round-up Lakes. The abundance of P. bellus is negatively correlated with all indicators of concentration, showing a decided preference for low pH values (a correlation coefficient of -.937) (Table V). FIGURE 6 The emergence of adults of Procladius bellus (Loew) and Procladius freemani Sublette from the one meter depth zone of several lakes. The ordinate is a logarithmic scale. Collecting began on May 19, took place every fourth day and terminated on August 29, 1970. PROCLADIUS BELLUS EAST L. BOX 27 M " J ' J ' A ' ' M"1 J "' J ' A J PROCLADIUS FREEMANI ROUND-UP L. L. LYE BOITANO L. M • J ' J ' A ' ' M ' J ' J A ' ' M ' J ' J ' ROCK L. BARKLEY L. EAST L. 10 J M A M A M 36 The only previous record of this species in British Columbia is from Cranbrook (Roback, 1971). Further discus• sion of general distribution and ecology of the species may be found in Wurtz and Roback (1955), Morrissey (1950) and Davis (1960). b) Procladius freemani This morphologically variable species can tolerate most environmental conditions found in the lakes (Table V) although it is most abundant in the upper salinities where its emergence displays striking differences among the lakes (Figure 6). In Barnes L. there is a small emergence of 4 per square meter in late May; in Round-up L. a larger emergence at this time is followed by another in early August. This latter pattern is repeated in L. Lye.with the addition of a substantial late June-early July emergence of 30 per square meter over 20 days. The one emergence peak in Boitano L. is as in Barnes L. (late May) but is much larger, consisting of 75 per square meter. In Rock Lake, a large, single peak of emergence occurs in late June-early July. East Lake, the only relatively fresh waterbody supporting large numbers of emerg• ing P. freemani has a peak in late May and one in late July. Box 17 and Greer L. show small, single peaks in the June-July period; Near Opposite Crescent and Barkley L. in early August. Thus it is seen that P. Freemani emerges at three times during the sampling period: late May, late June-early July and early FIGURE 7 The emergence of adults of Procladius dentus Roback from the one meter depth zone of several lakes. The ordinate is a logarithmic scale. Collecting began on May 19, took place every fourth day, and terminated on August 29, 1970. 37 BARNES L. ROUND-UP L. L. LYE 100 cc Ul p- ui 5 10 J in ec < o to cc Ul a. 1 1 1 I 1 1 1 I "~1 1 I I MJJAMJJA MJJA Z (3 CC Ul £ Ul BOITANO L. WESTWICK L. EAST L. 100 q 3 a < u. O cc Ul 10 CO Z r M M J J A M A 38 August. Every combination of these emergence times is recorded except for the sequence of June-July, early August. Why there is such disparity between the life cycles in each lake is not easily understood; no doubt it is best explained as the result of variation in the insects or the lakes. The species has seldom been collected at the extremities of its range. The only available record from British Columbia is a series of three males from Terrace (Roback, 1971). c) Procladius dentus This distinctive species has not been previously reported in British Columbia (Roback, 1971). In all the lakes in which it occurs in this study, P. dentus has a single generation emerging in late May (Figure 7). It has a preference for the more saline lakes (conductivity above 4000 jumho/cm) such as Boitano L., L. Lye, Round-up L. and Barnes L. The abundance of P. dentus is highly correlated with conductivity (p<,.01), total dissolved solids (p<.05), sodium (p<.05), HCO3 (p<.05) and S04 (p < .01) (Table V). d) Procladius clavus This is a recently described species (Roback, 1971) and is recorded previously only from the Northwest Territories. There is no doubt that P. clavus is the most abundant species of the genus in the lakes. Although it is restricted to 39 Boitano L., L. Lye, Round-up L. and Barnes L., P. clavus is very abundant. In Barnes L. most of the Procladius larvae are probably of this species, making it the dominant chironomid predator of that lake. P. clavus has a life cycle characterized by an extended emergence period occupying the entire month of June and the first week in July. The emergence in this period amounts to about 345 per square meter (Figure 8). The emergence in Round-up L. is a little less concerted and in L. Lye a second peak appears lasting from late July to the end of August. The emergence in Boitano L. occurs in the June-July period, but is much smaller in size. The significance of the second emergence peak in L. Lye is not known. The basic pattern in the other lakes suggests that a large emergence of adults developing from overwintering larvae produce a new generation of larvae that overwinter, but which may emerge early (L. Lye) depending on the conditions in the lakes. Alternatively, this second emergence may be a result of part of the overwintering larval population extending diapause, or even the occurrence of alternating generations. At any rate it is evident that P. clavus is an important member of the more saline environment, and seems entirely adapted to the sodium carbonate-bicarbonate lake type. Table V shows the highly significant correlation (p < .01) of abundance with conductivity, T.D.S., sodium, CO^ and HCO3. FIGURE 8 The emergence of adults of Procladius clavus Roback and Ablabesmyia peleensis (Whalley) from the one meter depth zone of several lakes. The ordinate is a logarithmic scale. Collecting began on May 19, took place on every fourth day and terminated on August 29, 1970. 40 PROCLADIUS CLAVUS BARNES L. ROUND-UP L. L LYE 100 q 10: CC UJ H LU s M M J J A LU M 10 J -i i 1 •—i 1 1 i r 1 -I-* 1 MJJA MJJA MJJA 41 e) Ablabesmyia peleensis This is an uncommon, but distinctive inhabitant of the fresher lakes. It appears to have two generations in the very fresh waters of Box 27 (conductivity 40 jumho/cm), one in late May-early June (30 per square meter) and one in July-August (Figure 8). In the most saline waters of its range (Barkley L., 600-700 umho/cm), Ablabesmyia peleensis has only one emergence peak in July, while in East L. the peak is in the late May-June period. The abundance of A. peleensis is negatively correlated with all environmental factors except disssolved oxygen and especially shows a definite reciprocal relationship with pH (r= -.938; p < .01) (Table V). Roback (1969) describes the food of the larvae. This species has not previously been recorded from British Columbia (Roback, 1971). f) Cricotopus flavibasis This common species of the Orthocladiinae reaches its greatest abundance in East L., but is found in most lakes up to a conductivity of about 7000 umho/cm (Round-up L.). It is the species determined in Cannings (1970) as Psectrocladius flavus, and is a denizen of aquatic plants. The paucity of this species in benthic samples in the present study further confirms that this species occurs on aquatic vegetation. The fact that the Orthocladiinae (without haemoglobin) are considered to be the group most sensitive to oxygen deficiency (Brundin, 1951; Buck, 1953) and their resulting occurrence near the surface 42 provides a possible reason for the absence of this subfamily in benthic samples and the appearance of larvae in the emergence traps. Cricotopus flavibasis has two generations, one emerging in late May, the other appearing as adults in late June-July. This second generation is most distinct in East L. and Near Phalarope (Figure 9). In the two lakes representing the upper ranges of its salinity tolerance (Round-up L. and L. Lye), C. flavibasis has another emergence peak from mid to late August (Figure 9). This emergence does not appear in fresher lakes; whether or not it is a result of adaptation to high salinities in the late summer is not clear. There is a great paucity of records for C. flavibasis in the literature. The only record available is that of Malloch (1915) who described the species from Illinois. Thus it seems C. flavibasis is new to at least B.C. and perhaps Canada. g) Cricotopus albanus This very small species was collected only in the four lakes having conductivities less than 800 ^imho/cm (Box 17, Barkley L., East L. and Box 27). This distribution, however, seems to be more closely associated with low pH; the cor• relation is highly significant (p<.01), r being -.900 (Table V). Correlations with all other solutes and measures of salinity are not significant, but are negative in sign. FIGURE 9 The emergence of adults of Cricotopus flavibasis Malloch and Cricotopus albanus Curran from the one meter depth zone of several lakes. The ordinate is a logarithmic scale. Collecting began on May 19, took place every fourth day and terminated on August 29, 1970. 43 ROUND-UP L. BOITANO L. NEAR PHALAROPE 100 10 LU UJ LU cc < o EAST L. CRICOTOPUS BOX 27 CO 100 cc FLAVIBASIS LU Q. O z o 10 J CC LU 2 LU (/) / CRICOTOPUS b ZD ALBANUS a < T 1 1 o cc 100 q BOX 17 BARKLEY L. EAST L. LU ca 10 1 * i i i 1 1— 1 1 r ~i 1 MJJA MJJA MJJA 44 Emergence is variable. In Box 27 there is a main emergence in late May and another peak in mid June. In East L. a single peak in late June-early July occurs. As the salinity increases emergence shifts to later in the summer (Figure 9). This is exemplified by a small emer• gence in mid July in Barkley L. and a similar peak in Box 17 followed by a much larger capture of adults in late August. Only one record (Curran, 1929) of this species is reported for Canada. h) Psectrocladius barbimanus This is the most common of the Orthocladiinae in the lake series. It varies in size and coloration and is notoriously variable in other morphological features (Wulker, 1956; Saether, 1967). P. barbimanus corresponds to Psectrocladius sp. B mentioned in Cannings (1970). Larvae were found in benthic samples, but much larger numbers were captured in the emergence traps along with pupae and adults. This species, especially in L. Lye, habitually built thin mud tubes on the sides of the emergence traps. The life cycle appears to consist of a single generation emerging in late May, although there are enough exceptions where a mid July emergence appears (East L., Barkley L., Near Phalarope, Boitano L.) to cast doubt on the idea of a single generation (Figure 10). Indeed, the later emergence in Boitano L. is sufficiently large to foreshadow the immense FIGURE 10 The emergence of adults of Psectrocladius barbimanus (Edwards) from the one meter depth zone of several lakes. The ordinate is a logarithmic scale. Collecting began on May 19, took place every fourth day and terminated on August 29, 1970. i 45 ROUND-UP L. L. LYE BOITANO L. 100 q cc 10 ui LU LU CC < O , , , ^ .v.r r-*-" n 1 w cc LU a. O z coc LU s LU L. JACKSON CO L. GREER BARKLEY L. b 100 a Q < U. O CC LU 03 3 10 Z J M M M 46 emergences in late July and August from L. Lye and Round-up L. (Figure 10). This July-August emergence in L. Lye represents a total of about 190 adults emerging per square meter. The histograms indicate that in the more saline habitats P. barbimanus is more abundant and tends to emerge later in the summer. It appears that in some lakes two generations may occur. That increased salinity is associated with a less synchronized emergence is evident from the significant (p<.01) correlation (Table VI). Psectrocladius barbimanus has been reported only once before in North America. A.L. Hamilton collected 5 males and pupal exuviae (Houghton, Sask., May 5, 1967) from a saline prairie slough of specific conductivity 2300 |imhos at 7.4°C (Saether, 1969). This represents an equivalent reading of about 3400 jumhos at 25°C, or approximately the conductivity of L. Jackson or Boitano L. Mundie (1957) reports P. barbimanus as an uncommon emerger from the 1 to 3 meter zone.from late April to late May in Kempton Park East Reservoir, London. i) Cryptotendipes ariel This is a species described by Sublette (1960) from Californian material. As far as can be established, it has not been reported elsewhere. C. ariel is restricted to the four most saline lakes in the series (conductivity '> 4000 umho/cm) (Figure 11). In all but Barnes L. there are two generations, one emerging in late May-early June, the other in FIGURE 11 The emergence of adults of Cryptotendipes ariel (Sublette) and Calopsectra gracilenta (Holmgren) from the one meter depth zone of several lakes. The ordinate is a logarithmic scale. Collecting began on May 19, took place every fourth day and terminated on August 29, 1970. 47 BARNES L ROUND-UP L L. LYE 100 : 10 : CC LU 1 r UJ 1 2 Ul cc < BOITANO L. CRYPTOTENDIPES / BARNES L. o 30 ARIEL / N U z 10: i —r— 1 1 M M J J A M J J A 48 August. The numbers in Boitano L. and L. Lye are small, but in Round-up L. a very large emergence (500 per square meter) appears in late July through August after a small (overwinter• ing population) adult emergence in May. In Barnes L. the August emergence is completely lacking and the considerable late May emergence carries over well into June. Table VI shows the tendency of the emergence pattern to spread over a longer period as the conductivity increases (r= .914 ; p < .01). The possibility exists that the increasing salinity of Barnes L. during the summer evaporation period prevents the larvae of the summer generation from developing rapidly enough to emerge before September. j) Calopsectra gracilenta This species of the old Tanytarsus (sens.lat.) genus is the most abundant species collected in the traps. The late May-early June emergence in Boitano L. alone reached a density of about 1000 per square meter (Figure 11). In L. Lye there is a maximum of three generations, the emergences increasing in size as the season progresses. In Boitano L. only a slight emergence occurs in early July after the major May emergence. In Round-up L., C. gracilenta repeats the L. Lye pattern with• out the June-July emergence. In Barnes L. the numbers are very small, only 12 per square meter emerging in very late June. C. gracilenta is a circumpolar species, in North America being reported only from Ellesmere Island (Oliver, 1963), 49 Baffin Island (Oliver, 1964) and Ellef Ringes Island (McAlpine, 1964). The species is also known from continental and arctic Europe (Lindeberg, 1968). In Finland it has been taken from the Gulf of Bothnia in shallow brackish water (3-4 °/oo) but has not been collected at Tvarminne (6 °/oo) (Lindeberg, 1968). For comparison, Barnes L. has a salinity of 10 u/ oo, so that it appears C. gracilenta can inhabit waters more saline (and probably warmer) than previously reported. Lindeberg (1968) also reports an Icelandic population with a July emergence peak. k) Derotanypus alaskensis This is a very widespread boreal species. Roback (1971) gives no B.C. records although his map indicates the range probably extends over the northern half of the province. This is the dominant macropelopian in the lake series and probably represents a large part of the predaceous chironomid fauna. In the lake series D. alaskensis has been found in all lakes although emergence was not recorded in Barnes L. or Box 27. In all the lakes except Sorenson L. there is a late May emergence (Figures 12, 13). A very small emergence in late July-early August in Sorenson L. is accompanied by a drop in the fourth instar larval numbers from 400 to 200 per square meter. The lack of fourth instar larvae in late May indicates that a May emergence probably occurred in Sorenson Lake, but took place before May 19th when the traps were put in place. FIGURE 12 Larval abundance and adult emergence of Derotanypus alaskensis (Malloch) in L. Lye, Boitano L. and L. Jackson. A. Third ( ) and fourth ( ) instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by D. alaskensis larvae. o FIGURE 13 Larval abundance and adult emergence of Derotanypus alaskensis (Malloch) in Rock L., Sorenson L. and East L. A. Third ( ) and fourth ( ) instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by D.alaskensis larvae. 52 The overwintering fourth instar larvae are no doubt accounted for by this usually large emergence in late May. In the more saline lakes (Figure 12) there is an even larger emergence later in the summer. This represents 100 per square meter in L. Jackson from June 21 to July 27. The second generation emergence is delayed in the higher salinities perhaps owing to concentration increases as the summer progresses. The situation in Boitano L. appears to be intermediate although the larval abundance curve (Figure 12) suggests a three generation situation. In summary, D. alaskensis appears to have at least one generation per year in the fresher waters, while in more saline lakes, definitely two and in at least one case three (Boitano) generations occur. Figures 12 and 13 show D. Alaskensis is most abundant in mid summer, especially in July. In L. Lye it makes up 60 per cent of the chironomid community in early July, in Sorenson L., 25 per cent. Thus its effect on prey species, at least large ones, should be greatest at this time. In general, numbers of D. alaskensis are sparse in the fresher lakes. 1) Einfeldia pagana This is the most abundant of all the species collected in the lake series. In all lakes, owing to its relatively large numbers (fourth instar larvae alone sometimes exceeding 40,000 per square meter in Near Opposite Crescent), E. pagana 53 represents a large proportion of the fauna (Figures 14, 15). Numbers are lower in Westwick L. and Sorenson L. (500 to 1000 per square meter) while they are higher in medium-high and medium-low salinities (averaging about 10,000 to 11,000 per square meter). The larvae probably overwinter in the third and fourth instars; the first emergence of the year beginning in early June. In Figure 14 it is evident that these.emergences are very discreet (though occurring over 3 or 4 weeks). In the fresher lakes (Figure 15) a second generation emerges. The relationship between conductivity and the number of emergence peaks (-.424) (Table X) supports this fact. In the very fresh East L. the two emergence peaks are found on earlier dates again indicating that this species may develop more slowly in lakes of higher concentration. Similarly, Table VIII shows that the greater the percentage of E. pagana present, the lower the conductivity, T.D.S. and concentrations of sodium, HCO3 and CO^. In these cases the coefficients are -.639, -.614, -.658, -.645 and -.589 respectively where -.514 is significant at p <.05 and -.641 at p <.01. It is interesting that unlike other Einfeldia pagana larvae (Oliver, 1971 B), the larvae of E. pagana collected in this study lack ventral tubules in all instars. This phenomenon is also apparent in some larval types of Chironomus, notably C. salinarius where the same morphologi• cal species may possess or lack blood gills (0. Saether, pers. comm.). Since it is thought that these structures are 54 functional in osmotic regulation (Wigglesworth, 1933; Sutcliffe, 1960), it is possible that the lack of tubules is an adaptation allowing E. pagana to colonize more con• centrated waters than is usually the case. Wigglesworth (1933), who notes that dipterous species living in saline environments (both naturally and in experimental situations) tend to have reduced tubules, believes that the tubules are the only highly permeable areas of the body, and thus the resistance of larvae to high osmotic pressures will be favored by the reduction of these structures. Phillips and Meredith (1969), however, have shown that in the salt water mosquito Aedes campestris the anal papillae are morphologically similar to those in fresh water species and are probably able to actively transport ions in and out of the body. In most lakes the fourth instar populations are at their smallest from late June to early August. Throughout the summer the larval composition of E. pagana and Glyptotendipes barbipes shows an almost inverse relationship (Figures 14, 15, 16 and 17). This may be due to the fact that these two species are adapted to the same conditions. In lakes where they are abundant these two species make up almost 100 per cent of the individuals present. If the percentage composition of one increases, the percentage composition of the other decreases. That the two species are similarly adapted is evidenced by the correlation coefficients between their abundances (.808) (Table VII) and their per cent composition (.645) (Table VIII), both significant at p<.01. FIGURE 14 Larval abundance and adult emergence of Einfeldia pagana Meigen in L. Jackson, Rock L. and Westwick L. A. Third ( ) and fourth (——) instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by E. pagana larvae. FIGURE 15 Larval abundance and adult emergence of Einfeldia pagana Meigen in Near Opposite Crescent, Barkley L. and East L. A. Third ( ) and fourth ( —- ) instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by E. pagana larvae. 57 m) Glyptotendipes barbipes Found in all the lakes, G. barbipes shows sporadic occurrence in the higher salinities and is most abundant in the range from 500 to 3000 umho/cm. In these lakes it reaches a maximum of about 11,000 per square meter. The overwintering larvae emerge in late May in all lakes. In Rock L. and East L. this initial emergence extends into early June. A second generation emerges at different times in different lakes, usually in mid or late July. The situation in L. Jackson and in Rock L. (to a lesser degree) is somewhat different. It is not too clear whether the second emergence is a separate generation or simply the emergence of slower developing overwintering fourth instar larvae (Figures 16 and 17). The small August 29 emergence in East L. may be the beginning.of a larger third generation emergence. That G. barbipes appears to be more abundant and dominant in the lower salinities emphasizes the fact that the species has more generations in fresher waters. All correla• tion coefficients (Table VIII) measuring the relationship between percentage composition and conductivity (-.626), T.D.S. (-.613), sodium (-.628), C03 (-.543) and HCO3 (-.576) are significant at p<.05. The number of emergence peaks is negatively correlated with conductivity, T.D.S., sodium, C0o and HCOo (Table X). FIGURE 16 Larval abundance and adult emergence of Glyptotendipes barbipes (Staeger) in L. Jackson, Westwick L. and Sorenson L. A. Third ( ) and fourth ( —- ) instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by G. barbipes larvae. FIGURE 17 Larval abundance and adult emergence of Glyptotendipes barbipes (Staeger) in Rock L., Barkley L. and East L. A. Third ( ) and fourth ( — ) instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid community represented by G. barbipes larvae. Larval Composition ( % ) No. emerging per sq.m No. larvae per sq.m VO 60 The time of the main emergence is later in fresher waters; coefficients indicating this are significant at the 99 per cent level (Table XI). This is unlike the cases of E. pagana and D. alaskensis, but may result from adaptations to higher salinities. For example, it may reflect a tendency of G. barbipes populations to complete development early to avoid the higher salinities of late summer. In this context it should also be noted that in higher salinities the synchrony of emergence is greater than in lower ones (-.559) (Table VI). On the whole, G. barbipes is most abundant in mid summer (July) after fourth instar larvae have developed from the initial May matings. Throughout the lakes abundance is very significantly correlated to the abundance of D. alaskensis (.785) and E. pagana (.808) n) Chironomus anthracinus Although this species has been recorded from Alberta and California (Stone et al, 1956), there are no records from British Columbia. This is one of the three Chironomus species commonly found in the lake series. At one meter of depth the larval density ranges from 100 to 1000 per square meter. The species is evidently most characteristic of eutrophic profundals (Lundbeck, 1926; Berg, 1938) and is often regarded as an indicator of low oxygen conditions (Brundin, 1951). Since Topping (1969), calling it Chironomus sp. A, 61 showed C. anthracinus was prevalent at depths greater than two meters in the lakes under consideration, it is possible that the main population emergences were missed by the trapping in the present research, the populations sampled being peripheral ones. In the lakes where no May emergence is recorded it is possible that emergence occurred before the traps were placed in position. The low levels of fourth instar larvae in May in Boitano L. and Sorenson L. may indi• cate this. The species is not obvious in Rock L. Although it appears that C. anthracinus usually has one generation, emergence patterns are extremely variable(Figures 18 and 19). This is in accordance with Thienemann (1951) who recorded variations in the time of year C. anthracinus swarmed at a north German lake. Mundie (1957) found the species univoltive in Stains South Reservoir, London, where April emergences predominated although some September adults were caught. In Lake Esrom, Denmark, Jonasson (1954) found a month- long emergence period with a mode on May 10, 1954. In the lakes studied herein, the amount of C. an thrac inu s emergence is correlated with the concentration of magnesium (p<.01) (Table IX). In Rock L., C. anthracinus makes up a major part of the chironomid fauna in July and August (Figure 18). Levels at one meter in Westwick L. and Sorenson L. are low (Figure 19). The species is most abundant in the habitats preferred by E. pagana (Table VII). FIGURE 18 Larval abundance and adult emergence of Chironomus anthracinus Zetterstedt in Boitano L., L. Jackson and Rock L. A. Fourth instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by C. anthracinus larvae. FIGURE 19 Larval abundance and adult emergence of Chironomus anthracinus Zetterstedt in Sorenson L., Barkley L. and East L. A. Fourth instar numbers per square meter taken at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by C. anthracinus larvae. 0 Larval Composition ( /o) No. emerging per sq.m No. larvae per sq.m 64 o) Chironomus n. sp. This is a hitherto undescribed species that keys out near C. atritibia Malloch in the keys of Townes (1945). It will be described by Sublette who is now revising the North American Chironomus using giant chromosome characters. Bassett (1967) called this Chironomus species his Species V and noted that its chromosomes displayed extensive pairing between centromeres. This, along with other characters such as banding pattern, separates the new species cytologically from similar species like C. anthracinus (Bassett's Species IV). The species was recorded by Topping (1969) under Chironomus sp. B as being most abundant below a depth of two meters. It is the most common of the Chironomus species in the lakes; moreover, its tolerance of high salinities is much greater than that of other members of the genus considered herein. Indeed, this species reaches its greatest abundance in Barnes L. (Figure 20) where it is by far the dominant nonpredaceous chironomid. The species makes up almost 100 per cent of the fourth instar chironomid fauna in late summer. Table VII shows the relationship between the abundance of this species and ion concentration. Correlations with conductivity, T.D.S., sodium, carbonate and bicarbonate concentrations are positive (p<.01). The correlation with the concentration of sulfate is significant at p<.05. In most lakes the initial emergence occurs in May. In Sorenson L. the lack of fourth instar larvae in May suggests 65 an early emergence. Here there is an August emergence as well. In Barnes L. all the adults emerging from May to early July probably are from the same overwintering genera• tion. A portion of the fourth instar population may prolong diapause and not emerge until June and early July. The recruitment of the new generation third instar larvae into the ranks of the fourth instar keeps the level of the latter rising even though considerable emergence is occurring. The majority of new generation larvae are not fourth instar size before the middle of July, however, so that emergence before this time is almost certainly due to overwintering adults. Thus all adults appearing after mid July are probably of the new generation, and the drop in fourth instar larvae numbers at this time (10,000 down to 5,000 per square meter) is a re• sult of this emergence. It is probable that the remaining fourth instar larvae overwinter alone in Barnes L. (since it is unlikely that another generation of fourth instars can be produced during the short fall) or with second or third instars. If the smaller instars do manage to overwinter, they may be the individuals emerging the next year in June, the overwinter• ing fourth instars emerging in May. In some of the lakes (Boitano L., L. Jackson, Rock L. and East L.) only one genera• tion is observed (Figures 20,21 and 22). As previously mentioned, this new species of Chironomus is particularly interesting because of its unique domination of Barnes L., the most saline lake (conductivity about 12,000 umho/cm) in the study. The other species of Chironomus were FIGURE 20 Larval abundance and adult emergence of Chironomus n. sp. in Barnes L., Boitano L. and L. Jackson. A. Fourth instar numbers per square meter at weekly intervals. B. Adult emergence: numoers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by Chironomus n. sp. larvae. Larval Composition (%) No. emerging per sq.m No. larvae per sq.m FIGURE 21 Larval abundance and adult emergence of Chironomus n. sp. in Rock L. and Sorenson L. A. Fourth instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by Chironomus n. sp. larvae. FIGURE 22 Larval abundance and adult emergence of Chironomus n. sp. in Barkley L. and East L. A. Fourth instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larvae chironomid population represented by Chironomus n. sp. larvae. 69 not collected here, although two unidentified larvae of different species, Chironomus sp. C and Chironomus sp. D occur in very low numbers (Table IV). The great abundance and large emergence of this Chironomus species in Barnes L. is probably due to both its successful adaptation to the chemically rigorous environment and to a considerable reduction in competition from similar species. It is notable that the per cent composition and abundance of this species are correlated with the index of diversity (Tables VII and VIII). The emergence pattern differs from that in lakes where C. anthracinus, C. tentans and C. plumosus occur. The tendency for the emergence pattern to spread out in habitats having a high index of diversity is reflected in the correlation coefficient -.603 (p<£.05) (Table VI). p) Chironomus tentans This species is common, but not abundant in the middle range of conductivities from 500 to 3000 jumho/cm. It occurs in Boitano L. (conductivity 4108 umho/cm) in only very small numbers. In most lakes the density of fourth instar larvae never exceeds 300 per square meter, making the species only a minor component of the community as far as percentage composi• tion is concerned (Figures 23 and 24). C. tentans has its greatest development at one meter in Sorenson L. where fourth instar larvae number 1000 to 1500 per square meter. These relatively low densities, however, are sufficient to enable 70 C. tentans to comprise 35 per cent (Westwick L.) and 50 per cent (Sorenson L.) of the chironomid fauna. The amount of emergence is small in most lakes, usually under 10 per square meter and usually occurs in late May. In Westwick L. this May emergence is spread over 28 days and represents an emergence of about 20 adults per square meter over 4 days directly after the traps were set; there• fore this may be the end of a larger emergence beginning earlier. In the late July emergence this trend is reversed, Westwick L. having 2 per square meter over 20 days. The number of days between the medians of the emergence peaks in Westwick L. is 56, in Sorenson L. 68 and in Rock L. 37. At o 25 C in the laboratory the insects have been reared to the adult in 44 days (16 hours light, 8 hours dark) (Pat Collen, pers. comm.) and at the same temperature Sadler (1935) reported generations of 35 to 45 days. Chironomus tentans begins development when the water temperature reaches 10°C (Sadler, 1935; Acton, pers. comm.). The number of accumulated degree days between the first date on which 10°C was recorded and the date of the initial emer• gence may thus be calculated (Table XIII) using Figure 5. o j 10 C was reached during the last days of April and the first days of May and the first recorded emergences began in the third and fourth weeks of May (Table XIII). The accumulated day degrees for the development of the overwintering fourth instar larvae amount to 249.75 in Westwick L., 266.0 in Sorenson L. and 441.25 in Rock L. The fact that the second 71 emergence peak came most quickly (37 days and 648.25 day degrees) in Rock L. is rather surprising. The interpretation that the July emergences in L. Jackson, Barkley L. and East L. are due to the progeny of overwintering larvae is being taken. The low or decreasing numbers of fourth instar larvae in late May indicate that emergence probably occurred before May 19. It is possible that emergence in these three lakes was postponed because of serious competition or lack of favored food. There being little or no difference in temperature regimes and day length changes among the lakes, these variables can hardly be the cause of differences in developmental rate. Other factors must be producing variation in the life cycle of C. tentans. The only physico-chemical parameters correlating with abundance and per cent composition of C. tentans are oxygen and organic carbon levels. Dissolved oxygen correlated with abundance at -.578 (Table VII) and with per cent composition at -.651 (Table VIII). There is a relationship between organic carbon and abundance (.547) and per cent composition (.648). Although the abundance of C. tentans is related to environmental factors influencing other species in similar ways, there is no clear cut relationship between the abundance or percentage composition of C. tentans and that of potential competing species. 72 C. tentans abundance in May, however, is correlated with the May abundance of C. anthracinus and Glyptotendipes barbipes. This may have further influence on subsequent spacing of emergence periods. There are three groups of predaceous chironomids that may affect C. tentans - the several Procladius species, Derotanypus alaskensis and Cryptochironomus psittacinus. No significant relationship between these predators and C. tentans (regarding abundance or per cent composition) is suggested by the correlation studies (Tables VII and VIII). As expected, the amount of emergence throughout the summer is dependent on the abundance of the larvae (.536). This is further characterized by the correlation of the July emergence with the abundance (.762) and the percentage com• position (.710) of larvae present in June. In addition, the amount of May emergence determines the abundance of larvae in June (.590) and July (.670) as well as the June (.841) and July (.992) percentage composition. These are very basic results reflecting the generation time of C. tentans. The number of emergence peaks is correlated with abun• dance (.586) and per cent composition (.703) throughout the summer. In May the coefficient is .589 and in July it is .724. The initial May emergence and the index of diversity for May are correlated (r.540), the emergence being much larger in lakes having lower diversity. 73 The emergences of C. tentans never occur at the same time as those of C. anthracinus and n. sp. In Sorenson L. , for example, where at one meter C. tentans is completely- dominant, a late May C. tentans emergence can be compared to the initial emergences of C. anthracinus and n. sp. in mid June. In Westwick L. the large C. tentans emergence lasting from May 19 to June 13 (Figure 23) and the small July peak are the only emergences of the three species in the lake. Similar instances can be seen in Figure 28. Table XII shows that when larval numbers of C. tentans are high, the emergence times of C. anthracinus tend to occur later in the summer (.566). Similarly, when the num• bers of C. anthracinus are high, C. tentans emerges later (.597). FIGURE 23 Larval abundance and adult emergence of Chironomus tentans Fabricius in L. Jackson, Westwick L. and Sorenson L. A. Fourth instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by C. tentans. larvae. L. JACKSON WESTWICK L. SORENSON L. FIGURE 24 Larval abundance and adult emergence of Chironomus tentans Fabricius in Rock L., Barkley L. and East L. A. Fourth instar numbers per square meter at weekly intervals. B. Adult emergence: numbers per square meter taken every fourth day. C. The percentage of the total larval chironomid population represented by C. tentans larvae. No. larvae per sq.m Larval Composition ( % ) No. emerging per sq. m _ TABLE V Summary of correlation coefficients describing the relationship between environmental factors and the amount of emergence of certain species, r = 0.514 is significant at p=.05; r = 0.641 at p=.01. Conduct• „ % organic Mg CO, HCO. SO, p ivity T.D.S. Na carbon Procladius bellus .302 -.292 -.247 ,388 -.193 -.345 ,291 .074 -.937 -.126 Procladius freemani .179 .154 .171 .019 .022 .184 .222 .156 .221 -.094 Procladius dentus ,652 .640 .629 .073 .491 .598 ,642 .156 .346 -.086 Procladius clavus ,910 .904 .930 .288 .858 .903 .472 .257 .415 -.200 Cricotopus flavibasis .190 -.196 -.163 .239 -.173 -.136 .252 .019 -.101 -.139 Cricotopus albanus ,362 -.351 -.302 .423 -.224 -.386 .375 .171 -.900 -.169 Psectrocladius ,272 .230 .275 .164 .104 .381 .092 .060 .201 -.016 barbimanus Cryptotendipes ariel .465 :447 .473 -.171 .293 .449 .199 .151 .275 -.079 Calopsectra gracilenta .219 .199 .173 .289 .024 .167 .473 .020 ,169 .099 Ablabesmyia peleensis ,318 -.308 -.258 -.432 -.207 .345 -.325 .091 ,938 -.210 TABLE VI The correlation between emergence histogram dispersion and environmental factors. Non parametric statistics. Significance with p 0.05 is marked * and p 0.01 **. SPECIES CONDUCTIVITY INDEX OF DIVERSITY Derotanypus alaskensis -0. 310 -0. 134 Einfeldia pagana -0. 314 -0. 253 Chironomus tentans -0. 365 -0. 005 Chironomus n.sp. 0. 423 -0. 603 * Chironomus anthracinus -0. 397 0. 075 Glyptotendipes barbipes -0. 559 * 0. 024 Procladius freemani 0. 213 0. 021 Procladius bellus -0. 390 0. 009 Procladius clavus 0 747 0. 267 Procladius dentus 0 619 0. 121 Calopsectra gracilenta 0. 777 +0. 206 Psectrocladius barbimanus 0 838 ** -0. 441 Ablabesmyia peleensis -0 .439 -0. 220 Cricotopus flavibasis -0 185 0. 248 Cricotopus albanus - .403 -0. 046 Cryptotendipes ariel 0 .914 -0. 025 TABLE VII Summary of correlation coefficients describing relationships between environmental factors and species abundance. r=0.514 is significant at p=.05; 0.641 at .01. Procladius n.sp. species Remainder psittacinu Cryptochironomus barbipes Glyptotendipes an Chironomus Chironomus alaskensis Total Mg Chironomus Einfeldia Chironomids 7. tentans pagana HC0 Derotanypus Biomass Diversity Na Index PH °2 so C03 T.D.S. Conductivity Call Organic thracinus 4 3 species) No. of of Carbon s -.237 -.186 -.075 1.000 .213 .378 .689 .386 .291 .708 .260 .489 .077 .329 .289 .227 .537 .706 .972 .940 .993 .998 Conduc tivity -.279 -.203 1.000 -.064 -.371 -.284 -.272 -.471 -.095 -.306 -.202 .182 .336 .671 .740 .531 .316 .723 .962 .949 .991 T.D.S. -.374 -.258 -.309 -.102 -.481 -.332 -.223 -.251 -.246 1.000 -.190 .204 .371 .709 .717 .485 .305 .632 .981 .955 2 -.041 -.070 -.340 -.098 -.252 -.096 -.022 -.032 -.133 1.000 -.226 -.220 .126 .095 .048 .417 .497 .358 .555 -.399 -.274 1.000 •,350 -.215 -.251 -.431 -.175 -.244 -.147 .010 .598 .172 .863 .412 .261 .586 .933 0 (J Summary of correlation coefficients describing the relationship between environmental factors and species per cent composition. r=0.514 is significant at p=.05; r=0.641 at p=.01. 3 o rt 3" o3" a w a w H- ro3 H- 3 B> 1 H a >-< Q> M> 01 o • O m o 3 111 ?r rt 3 3 t-> til Ul o a. ro3 3 R 3 01 H- 2W tcn 01 2g LO ON Ln M Conductivity 00 *o ro T.D.S. •p- H* Na LO Mg O •P- •p- CO, ON .p- HC0-, .p- SO, •p- pH •P- % Organc C. 00 Index of ON r—• Diversity Biomass Total no. o ro chironomids 03 Derotanypus LO .p- ro LO ro .p- LO LO VO o ^1 oo o alaskensis VD 00 I-*1 •p- ro Lo ON 1 1 1 1 • 1 I-1 Einfeldia ON ON ON o ro O o Parana ro Ln •P- . •P- vo CO o •P- VO 00 Ln VO ON •p- o i 1 1 1 1 >-• ro t—' LO O o M o Chironomus J> i> LO LO *o o Ln 00 VO Ln ON LO o 1 1 1 Chironomus ro ro o ro o O n. sp. LO ON 00 O VO . 4> LO Co o 1 1 . I 1 h- Chironomus ro ro ro to O anthracinus •p- •P- ro 4> O Ln •P- ON vo O 1 i i Clyptotendipes *J ON «o O fr-*E- ro •p- O Ul VO 00 O barbipes M Procladius oo 00 O 00 CO O (all species) NO 00 O Cr yptoch ironomus o o PKittacxnus o Remainder of species 6L TABLE IX Summary of correlation coefficients describing the relationship between environmental factors and the amount of emergence. r=0.514 is significant at p=.05; r=0.641 at p=.01. o 3 q rt O rj 3* n> 3" P p- H- tn 3 w 3 M X) rr Co t-n O o (U 0 3 ro 3 3 3 3 ft) Q Q CO Q a c C P> 2CO co Conductivity LO M LO >-> N> T.D.S. Na Mg CO, HCO, SO, pH o O r—1 Ln t-1 »-» % Organic \D Ln O Ln IO a* h-* O Lo LO o Carbon 1 1 r—1 Derotanypus Co O o o to LO 4> JL>O o alaskensis 00. ro ro a* o Einfeldia pagana Chironomus tentans Chironomus n. sp. Chironomus anthracinus Clyptotcndlpes barbipes 08 TABLE X Summary of the correlation coefficients describing the relationship between environmental factors and the number of emergence peaks for various species. r=0.514 is significant at p=.05; r=0.641 at p=.01. o 3 rt o o PI rr rr Hi H* p- tn H- ;o 3 H fT Conductivity T.D.S. 1 * 1 i * 1 OJ OJ o Na o cr. Cn cr. to CO Cn to ON 1 O.J . O H1 *-j Ln r-Oo« Ui -P- Mg ON cr> OJ ro J> 1 1 i 1 a* OJ to ro to O Cn Co CO to C03 h-» l-» CO o i 1 r 1 t ( o> OJ H» OJ OJ o HCOq ro Ln vo J> VO O CO IO 1 1 I OJ O OJ S04 . o o O CT. yo CO h-* 4> ON o J> ON 1 i .1 . o o OJ o to Cn o to Ui ON to J> to CO .O . . I-1 o to cr> yD o> Cn *-* PH to Cn H1 Cn o % Organic o 00 Carbon Derotanypus o alaskensis o Einfeldia pagana Chironomus o tentans o o Chironomus 00 o o n. sp. Chironomus o o anthracinus o ciyptot endlpes barbipes 18 TABLE XI Summary of correlation coefficients describing the relationship between environmental factors and the times of major emergence in several species. r=0.514 is significant at p=.05; r=0.641 at p=.01. o 3 L n rt o O m rD rr H« w H' 3 H* 3 <~t a H rr H P» O o l» 0 3 3 3 3 to di a o o (A O g Iw CcO CO Conductivity T.D.S. Na Mg o CO, •p- .p- LO o •p- ro t-1 HCOo 00 -p- CO LO t-< h-» vo ro o ro 1 1 i i t o ro o o o SO, ON CO ON CO Ln Ln cr* 1 1 ro o t-1 H» r-1 i—1 00 o VO Lo Ln ro LO Ln VO ro .M .o .ro r* (O LO PH O ON o Ln CO L0 •p- o vo ro I . .O• o • LO O ro % Organic vO to Ln VO Ln LO VO VO t~> Ov vo LO Carbon H» ro •P- ro H» O O Derotanypus VO CTN o Lo ON O alaskensis ON O vo O vo O I-1 Einfeldia 00 Ln Ln ro O ro ON •P- VO O pagana vO VO t-1 Ln o h-> Chironomus -P- 4> O •P- - Ln LO o tentans vO Ln Ln o I-" Chironomus LO ro O 00 Co O n. sp. ON ro o Chironomus anthracinus Glyptotendipes barbipe"s Z2 TABLE XII Summary of correlation coefficients describing the relationship between larval abundance, numbers of emerg• ing adults, number of emergence peaks and emergence time, r=0.514 is significant at p=.05; r=0.641 at p=.01. The developmental rates of C. tentans in various lakes. LAKE Date on which First Accumulated Second Accumulated 10°C was first emergence day degrees emergence day degrees reached begins between begins between 10°C and 1st first and emergence second emergence Westwick 29 April 19 May 249.75 27 July 1378.75 Sorenson 29 April 21 May 266.0 19 July 822.25 Jackson 30 April - - 3 July 2035.50 Rock 1 May 2 June 441.25 7 July 648.25 Barkley 1 May - - 19 July 1410.0 East 3 May - - 21 July 1296.0 85 5. The Chironomid Complex and the Lake Series In order to characterize the chironomid complex in the saline lake series and to clarify the relationship between C. tentans and other species, it is useful to describe the chironomid associations and group the lakes according to the dominant species present. Referring to Table XIV it is seen that the chironomid associations can be divided into three main groups : a) The Cricotopus albanus - Procladius bellus - Ablabesmyia peleensis association In the lakes studied this community is restricted to Box 27 where low salinity (mean conductivity 40 umho/cm and a T.D.S. level of 15 to 20 ppm) and low pH (6.4) are especially evident. The flora in this magnesium carbonate- bicarbonate lake is dominated by emergent plants, notably Potamogeton natans (Plate 1). It has a varied fauna with a relatively high index of diversity (2.14) (Figure 25). Although there is a high diversity, the density of larvae is the lowest in the entire lake series. The chironomid fauna is very distinctive. Only three emerging species are found: Procladius bellus (64%), Ablabesmyia peleensis (14%) and Cricotopus albanus (22%). The Cricotopus albanus larvae mine in Potamogeton leaves. P. bellus and A. peleensis are both free-living tanypodine predators. 86 b) The Glyptotendipes barbipes - Einfeldia pagana association These two species dominate the lakes having mean conductivity measures raning from 488 (East L.) to 2766 (L. Jackson) jumho/cm (Table I). The main predator is Derotanypus alaskensis. There is considerable variety in the species composition of the water bodies involved. For example, in Near Phalarope, large densities of non predatory, mud dwelling chironomids are lacking. The dominant species, Psectrocladius barbimanus, inhabits aquatic vegetation. Near Phalarope also contains the largest concentration of the predator Tanypus sp. found in the lakes. The species is known only from larvae in bottom samples (Table IV); whether or not it is Tanypus punctipennis (Table II) is not known, since no adults were trapped here. Nevertheless, Near Phalarope is included as a lake in this section because of its similarities to the other lakes involved. The group can be divided into three subgroups depending on the abundance of species secondary to G. barbipes and E. pagana in the following manner: (i) Cricotopus - Chironomus anthracinus subdivision contains species prominent in three lakes (East L., Barkley L., Box 17) having con• ductivities ranging from 488 to 741 umho/cm and T.D.S. concentrations of 372 to 571 mg/1. The Orthocladiinae, especially the genus Cricotopus 87 are important. As well as being typical of the profundals of oligotrophic lakes (Brundin, 1951) the Orthocladiinae are often dominant in the littorals of eutrophic waters (Sandberg, 1969). j The genus Chironomus, represented especially by C. anthracinus, makes an appearance. This sub• division may be considered a transition between the unique freshwater species of Box 27 and the large middle salinity association dominated by G. barbipes and E. pagana. The Chironomus tentans subdivision includes species characteristic of conductivities from 810 to 1500 umho/cm (Near Opposite Crescent to RockL.). It reaches its most distinctive form in Westwick and Sorenson Lakes (1200 to 1500 umho/cm) whose most important features are high levels of organic carbon,low oxygen tensions, Najas beds in deep mud, Scirpus at the margins and large mats of Spirogyra. At 1.0 meter the characteristic chironomid is C. tentans. Chironomus n. sp. is characteristic of the most saline lakes dominated by G. barbipes and E. pagana - Lakes Greer and Jackson with an upper limit of 2766 umho/cm conductivity and 2.5°/oo salinity. Large blue-green algal blooms (Aphanozomenon) are common from June to September. 88 The major predaceous chironomid is the large Derotanypus alaskensis which reaches its greatest density in the higher salinities. The most interesting observa• tion concerning the G. barbipes - E. pagana association is the fact that the three species of Chironomus are found in all ten lakes, but at 1.0 meter each is most abundant in a particular group of lakes. Thus C. anthracinus reaches greater proportions in the fresher lakes, C. tentans in the medium salinities and C. n.sp. in the most saline lakes dominated by G. barbipes and E. pagana. c) The Calopsectra gracilenta - Cryptotendipes ariel association Above a conductivity of 4000 jumho/cm and a T.D.S. concentration of 3000 mg/1 an entirely new species composi• tion appears. This group of species is associated with conductivities up to 1200 umho/cm and mean pH readings from 8.9 to 9.3 (Boitano L., L. Lye, Round-up L. and Barnes L.). Calopsectra gracilenta is one of the dominant species of the above three less saline lakes. It tends to be replaced by Cryptotendipes ariel as the salinity increases. Chironomus n.sp. is the major component of the Barnes L. chironomid fauna (46%) and makes up 16 per cent of the emerging Boitano L. fauna. It is not abundant in Round-up L. or L. Lye. Derotanypus alaskensis is most abundant in L. Lye, but is largely replaced by Procladius clavus as the main predaceous chironomid in the high salinities of Round-up and Barnes Lakes. The biomass figures for this association of species with a high tolerance of saline waters are relatively low Although there are numerous species and large numbers of some species present, the larvae of these forms are small The indices of diversity for Round-up L., L. Lye and especially Boitano L. (2.74) are high. Barnes L. has the lowest index of all the lakes (0.90); certainly a reflec• tion of the lake's high salinity. The biomass is about 16 times that of Round-up L. principally because of the presence of large numbers of Chironomus n. sp. which reaches a considerable size. TABLE XIV The percentage composition of species in the lakes based on the total adult emergence May - August 1970. 90 Barnes L. Round-up L. L. Lye Chironomus n.sp. 46 Cryptotendipes ariel 47 Psectrocladius Procladius clavus 30 Calopsectra gracilenta 24 barbimanus :32 Cryptotendipes Psectrocladius Calopsectra ariel 17 barbimanus 6 gracilenta 28 Procladius dentus 4 Procladius clavus 10 Derotanypus alaskensis 25 Others 3 Others 13 Procladius clavus 9 Others 6 Boitano L. L. Jackson L. Greer Calopsectra Einfeldia pagana 35 Glyptotendipes gracilenta 71 Glyptotendipes barbipes '22 Chironomus n.sp. 16 barbipes 29 Derotanypus alaskensis 22 Procladius freemani 4 Derotanypus Einfeldia pagana 20 Derotanypus alaskensis 9 Chironomus n.sp. . 16 alaskensis 2 Chironomus n.sp. 16 Others 20 Others 7 - Others 11 Rock L. Near Phalarope Westwick L. Einfeldia pagana 37 Psectrocladius Einfeldia pagana 73 Glyptotendipes barbimanus 65 Chironomus tentans 19 barbipes 31 Cricotopus flavibasis 18 Glyptotendipes Derotanypus Glyptotendipes barbipes 4 alaskensis 15 barbipes 8 Psectrocladius Procladius .fr.eemani 7 Derotanypus alaskensis 5 barbimanus 2 Others 10 Others 4 Others 2 Sorenson L. Near Opposite Crescent Box 17 Glyptotendipes Glyptotendipes Glyptotendipes barbipes 29 barbipes 36 barbipes 65 Einfeldia pagana 23 Chironomus tentans 18 Einfeldia pagana 31 Chironomus anthracinus 20 Einfeldia pagana 18 Procladius bellus 1 Cricotopus albanus 14 PsectrocTadiiis Per o tanypu s~~ala s kens i s 1 Others 14 barbimanus 18 Others 2 Others 10 f Barkley L. East L. Box 27 Glyptotendipes Glyptotendipes Procladius bellus 64 barbipes 21 barbipes 29 Cricotopus albanus 22 Einfeldia pagana 21 Einfeldia pagana 25 Ablabesmyia peleensis 14 Psectrocladius Derotanypus alaskensis 23 barbimanus 12 Cricotopus flavibasis 11 Cricotopus Others 12 flavibasis 12 Others 34 91 C. DISCUSSION 1. The Chironomidae and the Lake Series It has long been known that the aquatic diptera (the Chironomidae in particular) represent one of the most diverse and adaptable freshwater groups. Suworow (1908) found a species of Chironomus in Lake Bulack on the Kirgiz Steppe in salinities of 285 °/oo, eight times the salinity of the sea. Chironomus plumosus is known to live in nature at a pH of 2.3 (Harp and Campbell, 1967). Such versatility makes chironomids ideal organisms with which to study the effects of variable chemical conditions on an assemblage of related species. Obviously, the chironomids in the lake series are adapted to their total environment. But what are the main factors determining the general distribution patterns described? In the past, chironomid distribution data has largely come from studies on the classification of the lake types using the dominant profundal chironomid fauna present (Brundin, 1949, 1951). An examination of this information in the context of the present research may lead to a better understanding of the factors influencing chironomid distribu• tion in the lakes. The classification of lake trophic types was first introduced by Thienemann (1920) and further developed in works by Lenz (1925), Lundbeck (1926) and Humphries (1936) for most of central and northern Europe. Brundin (1958) studied this concept on a greater scale and found that the classification, with regional variants in species, was valid the world over. This classification may be general• ized in the following manner. Oligotrophic lakes are usually dominated by species of the subfamily Orthocladiinae These are small forms lacking hemoglobin. Lakes becoming more productive (moderately oligotrophic) are more and more dominated by a Tanytarsus fauna, mesotrophic lakes contain proportionally larger profundal populations of the Chironomini (especially those without ventral tubules), whil the profundals of eutrophic lakes contain mainly large, hemo globin-bearing Chironomus species. These large larvae have ventral tubules and are represented by forms such as C. anthracinus and in the most eutrophic areas, C. plumosus (Brundin, 1958). Deevy (1942), Goulden (1964) and Stahl (1969) note that in stratified lake deposits the fossil chironomids often show a succession from Tanytarsus through to Chironomus, correlated with the lake's evolutionary sequence from oligotrophy to eutrophy. In one of his earliest papers on the subject, Brundin (1949) noted that the association of chironomids and trophic lake type is not direct, but is more a function of the annual minimum oxygen concentration that can be withstood by the larvae. Since hemoglobin is known to aid larvae in withstanding low oxygen conditions (Walshe, 1947 A,B, 1950; Harnish, 1960), the more hemoglobin present and the larger the size of the larva, the less difficulty there is in over- 93 coming the microstratification of reducing conditions on the surface of the sediment (Brundin, 1951). The supply of oxygen to the bottom of the lake is affected by the volume of the hypolimnion and the duration of stratification as well as the amount of decomposable organic matter in the hypolimnion. There is no rigid connec• tion between oxygen deficit and lake productivity since lake morphometry, among other things, complicates the situation. However, as Mundie (1957) explains, "It so happens that in very many lakes eutrophy is associated with a high oxygen concentration deficit and oligotrophy with a low deficit, so that a correlation between lake type and chironomid type emerges". A saline lake series, however, has never before been studied in this context. The similar morphometry and the lack of thermocline formation in the lakes under study (or at least the lack of hypolimnic effect on the depth zone under consideration) result in comparable oxygen concentrations throughtout the lake series. As oxygen would seem to have little influence on overall distribution patterns, an examination of product• ivity trends could be instructive. It might be expected that organic carbon would be a suitable measure of general productivity, with oxygen levels decreasing in areas of abundance much in the way oxygen deficits appear in highly eutrophic waters. Although organic 94 carbon and oxygen levels show an inverse relationship (Figure 26) (the correlation is -.649, p<.01), there is no indication that these parameters follow the general trend of increasing productivity with increasing salinity (Rawson and Moore, 1944). A high abundance of chironomids in Westwick and Sorenson Lakes might be expected, since the organic carbon levels peak there, but the larval den• sity is quite low. And in this case the low numbers are due to low densities of species that should be able to easily withstand the lower oxygen levels present. No indication that this paucity was due to increased predation was found. The photosynthetic activity in the lake series was not examined. Preliminary light and dark bottle studies have recently been instigated, however, and seem to indicate that the fresh and moderately concentrated lakes display three to five times the photosynthetic production of the very saline water bodies (Reynolds, pers. comm.). The lakes where, the G. barbipes - E. pagana association prevails have salinities ranging from 0.3 to 2.5 °/oo. These concentrations are not so high as to adversely affect primary production and con• sequently the lakes have a large phytoplankton stock and in most cases a peripheral belt of emergent vegetation. Such eutrophic conditions are ideal for the larger Chironomini. Moreover, there is some evidence that the fresher lakes are less productive than the moderately saline ones, according to Reynolds (pers. comm.). In Box 27 chironomids usually domi• nating the substrate of the lakes are conspicuously few, 95 while the Chironomus species are entirely absent. This is probably due to the lack of dissolved nutrients and a resul• tant low level of phytoplankton. Detritus and algae are the main food items of the larger tube dwelling species. Lellak (1965) and Jonasson (1954) note that the production of Chironomus species is dependent on:the amount of phyto• plankton in the water column. Amounts of dissolved solids in the water are often used as measures of productivity. In a larger number of British Columbia lakes Northcote and Larkin (1956) found that plankton and benthic fauna increased with increasing T.D.S., although the concentrations they considered were comparable to only the fresher lakes in the present study. Rawson and Moore (1944) examined a large number of lakes on the Saskatchewan prairie, some of which were similar to the lakes in the Cariboo-Chilcotin area. Again, a trend of increasing abundance of bottom fauna with increasing T.D.S. was observed up to a concentration of 2250 ppm. The number of bottom organisms decreased with increasing salinity past this point. A salinity of 2250 ppm approximates that of L. Jackson. Figure 25 shows the chironomid larval biomass in the lake series and reveals a similar decrease in benthic fauna above a concentration of 2250 ppm. The low levels in Rock L., Near Phalarope, Westwick L. and Sorenson L. are anomalous in this context. Indeed, a linear regression performed on the points in the graph showed the probability of the slope being FIGURE 25 Chironomid larval biomass and index of diversity for the larval complexes at 1.0 m in the lake series. INDEX OF DIVERSITY LARVAL BIOMASS (CM3/M2) CO NO o b b o o o o o o o o o Barnes L. Round-up L. L. Lye Boitano L. L. Jackson L. Greer Rock L. N. Phalarope Westwick L. Sorenson L. N. Op.Cres. Box 17 Barkley L. East L. Box 27 « FIGURE 26 Graph showing the relationship between oxygen levels and organic carbon in the lakes. PER CENT OF ORGANIC CARBON & 02 LEVELS (MG / L) rO 4v Ol o 00 -O _i _i _i i I Box 27 East L. Barkley L. Box 17 N.Op. Cres. Sorenson L. - Westwick L. - N. Phalarope Rock L. L.Greer L.Jackson Boitano L. L. Lye Round-up L. Barnes L. 98 zero was .29. It is possible that chironomid larval biomass alone is a poor indicator of relative productivity in lakes and that the inclusion of other benthic and planktonic organisms would alter the relative biomass results. In the lake series as a whole, it would seem that the basic distributional pattern is largely the result of inter• play between salinity and productivity. The very low densi• ties of larvae and the high diversity in Box 27 are notable, and in its chironomid fauna and chemistry the lake resembles an oligotrophic one. In salinities above that of Box 27 the species types change markedly and represent essentially a eutrophic lake fauna. Actually, all the lakes considered must be termed eutrophic, although if the arbitrary figure of Williams (1964) is adopted, only those lakes with a salinity of 3 °/oo (Boitano L.) and above can be classed as saline eutrophic like the lakes described by Decksbach (1924), Hutchinson (1932), Rawson and Moore (1944) and Bayly and Williams (1966). This demarkation applies nicely to this study since the change from a chironomid fauna typical of highly eutrophic waters to a community rather restricted to o , high salinities occurs at this 3 /oo salinity point. The biomass-diversity relationships in this transition are also important. Chironomid biomass in the eutrophic, blue-green algae rich L. Greer and L. Jackson is high, mainly due to large numbers of G. barbipes, E. pagana and C^n.sp. But because of this domination the numbers of species and the diversity are low. The biomass in the four lakes representing salinities above 3 °/oo is very low while the diversities in two of these lakes (Boitano L.j L. Lye) are higher than in any other lake - perhaps due to the presence of species that can tolerate high salinities as well as moderate ones. Although it is expected that rooted plants complicate any environment and encourage diversity by increasing niches and stabilizing interactions (Wohlschlag, 1950), the absence of rooted plants in these high salinity lakes does not seem to have a great effect on diversity. The very low diversity in Barnes L. is certainly a reflection of very high ionic con• centrations rather than the result of any reduced complexity owing to the absence of aquatic plants. Primary production in the higher salinities is reduced. This situation, along with the above mentioned productivity-diversity relationship in L. Greer and L. Jackson, reinforce MacArthur1s (1965) contention that an increase in productivity is not always accompanied by an increase in diversity. Where production is increased there is often a decrease in resource variety and a greater inequality of existing resources, tending to decrease diversity. The increase in chironomid biomass in Barnes L. is due to the high densities of Chironomus n.sp. which reaches a considerable size. The low numbers of this species in Round-up L. and Lye L. are not clear, but it would seem to be 100 something other than solute concentration. C. n.sp. occurs in greatest numbers where the diversity is lowest; this low diversity does not seem to be entirely a result of its owns high numbers. In similar situations, the absence from fresher water of a species adapted to high salinities is not due to hyporegulation difficulties, but is usually the result of biotic interactions leading to exclusion by other species (Beadle, 1943; Lauer, 1969; Scudder et al, 1972). FIGURE 27 Salinity tolerances of the identified species of the one meter depth zone in the lake series. Tartypus punctlpennls Derotanypus alaskensis — Derotanypus n.sp. Procladius bellus Procladius nietus Procladius freemani " Procladius ruris —— — Procladius dentus Procladius clavus . Procladius sublettei , Procladius n.sp. Ablabesmyia peleensis Nanocladius n.sp. Cricotopus albanus Cricotopus flavibasis —; _ Cricotopus trifasciatus Acricotopus nitidellus Psectrocladius barbimanus -. —— Psectrocladius zetterstedti - Psectrocladius n.sp. Chironomus anthracinus . Chironomus atrella — Chironomus tentans . Chironomus plumosus Chironomus n.sp.(near atritibia) Chironomus n.sp. Einfeldia pagana Cryptochironomus psittacinus Cryptotendipes ariel Endochironomus nigricans Glyptotendipe s barbipes 1 Polypedilum n.sp. Calopsectra gracilenta Calopsectra holochlorus i' 1 i : 1 1 1 0 3000 ' 6000 9000. 12000 Conductivity (umho/cm at 25°C) 102 2. Chironomus tentans and the Lake Series Topping (1969, 1971, 1972) has carefully examined the relationship between the distribution of C. tentans larvae and the physical and chemical environment, but little has been done to examine how these factors, along with biotic interactions, might affect the insect's life cycle. a) Physical and Chemical Influences C. tentans inhabits a substantial range of conditions (Acton and Scudder, 1971). It has considerable tolerance for saline waters and has been collected in the brackish waters of the Baltic (Palmen and Aho, 1966). In the study area its greatest abundance and emergence success occurs in the middle of the salinity range, particularly in Westwick and Sorenson Lakes. There is much variation in developmental time among the C.tentans populations inhabiting the six lakes under consideration (Table XIII). Comparing the lengths of the spring generation (second emergence) there is not real trend, although developmental times in Sorenson and Rock Lakes are substantially lower than the rest. The rapid growth of larvae in Sorenson L. supports the contention that this is the most favorable habitat for the species, but the situation in Rock L. is more difficult to understand. The brief developmental time (37 days) is consistent with rates report• ed by Sadler (1935), but is considerably, shorter than that in 103 neighboring populations. The postponed emergence of overwintering larvae complicates the situation further, and is possibly a result of a longer winter diapause or a majority of larvae overwintering in the third instar. Temperature is usually considered a primary factor in determining developmental rates (Miller, 1941; Mundie, 1957; Oliver, 1969, 1971). Hilsenhoff (1966) found that variations in the development of Chironomus plumosus in different parts of Lake Winnebago could be attributed to water temperature. Koskinen (1968) also recorded similar results for yearly variation in the emergence times of C. salinarius in northern Europe. There is no evidence that differences in generation times of C. tentans are caused by either variations in average temperature (Table II) or diel temperature range (Figure 4). Considerable work has been done on the effect of photo- period on the development of C. tentans. Englemann and Shappirio (1965) found that diapause at 22°C was maintained by short day periods (sixteen hours light). Clark (1971) recorded that low daylight regimes suppressed larval devel• opment and when such larvae were subsequently placed in long day length situations, emergence success was reduced. Members of the same population under identical tempera• ture and light regimes may show radically different develop• mental rates. Larvae hatching from the same egg mass often pupate two or three weeks apart (Collen, pers. comm.). Up to 90 per cent of fourth instars can fail to pupate and emerge during the time the rest of the population does. Numbers of these larvae will emerge along with the adults of the next generation (Clark, 1971). Similar asynchrony in C. tentans populations was established in the experimental pond populations studied by Hall et al (1970) and Fagan and Enns (1966) observed similar effects in populations of Glyptotendipes barbipes in sewage lagoons. In other insects, delayed hatching of eggs has been reported in the mayfly Ameletus lineatus (Gibbs, 1971) and this sporadic, asynchro• nous emergence brings all the advantages that accrue when the development of segments of the population is staggered. These include the survival of the population through periods of stress, the lessening of the impact of predation and the reduction of crowding and competition. It must be concluded that since there is little or no difference in the day length changes among the lakes, this factor can hardly be the major cause of differentials in the developmental rate of the various populations. C. tentans is most abundant in habitats associated with flocculant muds, detritus and stands of Scirpus. These conditions are especially well developed in Sorenson L. and Westwick L. and are associated with high levels of organic carbon (Table I). Since C. tentans is a detritus and algae feeder (Sadler, 1935), Topping (1971) used organic carbon as a measure of food abundance in these same lakes. Anderson 105 and Hitchcock (1968) and Palmen and Aho (1966) found that the numbers of Chironomus atrella and C. tentans respect• ively increased in the presence of organic material. In studies on the new Volta Lake Petr (1971) also noted that areas of high organic content were populated most abundantly by Chironomus species. It is possible, then, that the amount of organic carbon in the mud might be a reasonable measure of food availability. If the general conditions present in Sorenson L. and Westwick L. are associated with high levels of available food, the correlations between larval abundance and per cent composition of C. tentans and organic carbon may be meaningful. In controlled experiments, Hall et al (1970) found the developmental time of C. tentans larvae was markedly reduced in treatments with high food levels and that in such condi• tions the rate of emergence was increased. In the present study organic carbon levels were found to be correlated with the number of emerging adults and the number of emergence peaks. Sorenson Lake, with the largest amount of organic carbon, has a Chironomus tentans population that develops much more rapidly than the average. There is some indication, then, that the results reported by Hall et al (1970) may be applied to this natural situation. The same connection between the productivity of an environment and reproductive success is also reported in studies of the water bug Cenocorixa bifida hungerfordi (Jansson and Scudder, 1973). Females in 106 highly productive lakes developed eggs up to a month after females in less productive lakes ceased reproducing. The increase in organic carbon is accompanied by a decrease in the concentration of dissolved oxygen at the mud surface, resulting in a negative correlation between dis• solved oxygen and the abundance of C. tentans. Townes (1945), Gerry (1951) and Paine and Gaufin (1956) report that C. tentans prefers low oxygen levels to high ones and consider the species a good indicator of polluted water. b) Biotic Interactions The lack of negative correlations between the abundance of C. tentans and potentially competing or predatory species indicates there is little active separation of the populations in the one meter zone, either through differential reaction to physical and chemical factors or through behavioral activity. Further, the lack of positive correlations suggests that strong interaction between C. tentans and coexisting species is reduced. Nevertheless, it is interesting that three species of the genus Chironomus coexist in relatively large numbers in the one meter zone. The competitive exclusion principle has been formulated by many writers including Elton (1946), Hutchinson (1957) and Hardin (1960). DeBach (1966) summa• rizes the modern version: "Different species having identical ecological niches cannot exist for long in the same habitat". 107 In the case of C. tentans, C. anthracinus and n.sp., the ecological niches appear somewhat different. It has been shown that there is a general separation of the three species with regard to the lakes in which each is dominant, the implication being that the species have different preferences towards salinity or related factors. Further, Topping (1971) has observed that C. anthracinus and n.sp. increase in abundance with depth, showing greater densities in areas not inhabited by C. tentans. It is not clear whether this indicates some interspecific inter• action preventing C. tentans from actively living below two meters or whether it simply reveals different tolerances to environmental variation with depth. At any rate, in the one meter depth zone there is no indication of such strong sepa• ration. The fact that G^_n.sp. is so abundant in Barnes L. where C. tentans and C. anthracinus cannot exist may simply be a result of the insect living in its most favorable habitat rather than a result of decreased competition for food or space. But the opposite is suggested by other information. Although randomness was not tested, smaller standard devia• tions and the greater smoothness of the abundance curve indicate that Cj_ n.sp. is more randomly distributed in Barnes L. than in other lakes. Paterson and Fernando (1971) found that C. attenuatus and G. barbipes, probably through a behavioral mechanism, tended to become randomly distributed in a uniform environment when present in high densities. This was assumed to be a result of the lack of variation in the biotic (i.e. predation and competition) and abiotic environ• ment. Barnes L. is a good example of such a habitat and it is not surprising that similar results are found. It is also striking that in Barnes L. where C^n.sp. reaches numbers ten times those in any other lake, the predaceous D. alaskensis is very scarce. In L. Lye it is abundant while C^n.sp. is completely absent. Whether it is the high salinity or the reduced competi• tion that results in the asynchronous emergence of C. n.sp. from Barnes L. is unknown, but the latter is a possibility. Similar staggering of developmental times are evident in the case of C. tentans. The histograms show peaks occurring at different times from those of C. anthracinus and n.sp. although the patterns are not identical in each lake. That C. tentans, C. anthracinus and G. barbipes fourth instar abundances were correlated in May, but not afterwards perhaps indicates that a differential development rate after the May emergences is operating to keep the population peaks staggere A spacing of the life cycles of coexisting insects will reduc the intensity of competition for available resources (Ide, 1935; lilies, 1952; Corbet, 1964). Kajak et al (1968) showed that in experimental situations increased intra- and interspecific competition reduced the intensity of feeding, slowed down growth and increased mortality. FIGURE 28 Examples of the spacing of emer• gence times of Chironomus tentans and three coexisting species. A. Chironomus anthracinus B. Chironomus n.sp. C. Glyptotendipes barbipes 110 Other interactions can be inferred from the correla• tion studies. When the larval numbers of C. tentans are high the emergence times of C. anthracinus are delayed (and vice versa), perhaps indicating suppression of the develop• ment of the scarcer species. A dominant species likely has an advantage in obtaining food. The per cent composition of C. tentans is correlated with an increasing number of emer• gence peaks, suggesting a more rapid development in areas of greater dominance. C. tentans emergence is also much greater in habitats where the diversity of chironomid larvae is reduced. The evidence for ecological separation of C. tentans and its two relatives is not decisive, but there seems to be a mechanism (i.e. differences in diapause.length) by which emergence times, and thus maximum development periods, are staggered. That C. anthracinus and n.sp. are further separated from C. tentans by depth indicates this asynchrony may be important only in the peripheral parts of the habitat where contact is greatest. The problem of the separation of C. anthracinus and n.sp. is even more difficult. Emer• gence times are more closely linked (Figures 18 - 22); depth preferences are also similar. Chemical tolerances are dif• ferent, but in areas of coexistence the factors that allow the two species to live together are unclear. Correlation results show that Einfeldia pagana, Glyptotendipes barbipes and D. alaskensis inhabit the same type of habitat. Because it is the largest and most abundant predaceous chironomid in the lake system, D. alaskensis might be expected to influence the abundance of C. tentans. Owing to the large numbers of E. pagana and G. barbipes, these species are probably C. tentans' strongest competition (besides other Chironomus species) for food and space. The fourth instar larvae of D. alaskensis reach their peak abundance during early July.- This is the period during which the most serious predation on the larger chironomids might be expected to occur. At this time the majority of C. tentans larvae are also fourth instar. Since most litera• ture on the subject of Tanypodine food states that usually newly hatched chironomids or later instars of the smaller genera (Tanytarsus, Pagastiella) are eaten (Leathers, 1922; Armitage, 1968; Roback, 1969) perhaps the overall predation on C. tentans is small. The life cycles of G. barbipes and E. pagana are staggered; this enables both species to dominate the lakes of medium salinity. In Westwick and Sorenson Lakes densities of these two species are unusually low, whereas C. tentans makes up fifty per cent of the late summer chironomid fauna in Sorenson Lake. In the other lakes the large number of G. barbipesj E. pagana and to some extent the other Chironomus species creates a more intricate structure that likely restricts the success of C. tentans. What is the explanation for the low densities of G. barbipes and E. pagana in Sorenson and Westwick Lakes? If the two species do not thrive in low oxygen and high organic carbon conditions, then this would be sufficient to lower their numbers. But Gerry (1951) and Sturgess and Goulding (1968, 1969) have concluded that Glyptotendipes lobiferus and G. barbipes are more tolerant of anaerobiosis than Chironomus species. G. barbipes can survive anaerobi• osis about ten times longer than C. riparius (Sturgess and Goulding, 1968) although low oxygen conditions reduce its growth (Kimerle and Anderson, 1971). No pertinent informa• tion is available for E. pagana, but specimens kept in bottled mud and water were able to survive at least five days while Chironomus collections died after two days. The reasons for the lower numbers of G. barbipes and E. pagana in Westwick and Sorenson Lakes are not understood; neverthe• less, the absence of high levels of competition seems to play an important role in the existence of C. tentans in these lakes. 113 IV CHIRONOMUS TENTANS AND SOME BIOTIC FACTORS AFFECTING CHROMOSOME INVERSION A. MATERIALS AND METHODS 1. Background Topping (1969) has described the inversion frequencies in the salivary chromosomes of some of the same Chironomus tentans populations that the present study has analyzed. He concluded that the inversion frequencies differed significant• ly in different lakes, but did not differ within lakes. It is very important to note that the frequencies of the inversion 1 Rad (the inversion considered in this study) do not vary significantly either seasonally or annually (Acton, pers. comm.; Topping, 1969). The details of these and other chromo• some analyses may be found in Topping (1969). Topping notes, "The implication of the long term stability of inversions in chromosome 1 is that the inversions are adapted to relatively stable environmental factors". There• fore he attempted to correlate the inversion frequency with physical and chemical parameters. Surprisingly, none of these rather stable environmental factors correlated with inversion frequency; the only variable to do so was a biological one - the number of other chironomids in the environment. The long term stability of inversion 1 Rad enables Topping's data to be used in further, more detailed correla• tion studies. The variable "number of other chironomids" can 114 be divided into a number of more restricted biotic para• meters . 2. The U.B.C. Triangular Regression Package was again used in the correlation analysis. Unfortunately the use of a series of lakes in this study slightly differ• ent from the one examined by Topping precludes the direct comparison of correlations. Topping used twelve lakes for his analysis; only the eight lakes in the present study having inversion data are used here. 115 B. RESULTS Three environmental factors were found to correlate (p<.05) with the inversion frequency of 1 Rad (Table XVI). These are sodium concentration (.770), dissolved oxygen (.740) and the amount of organic carbon in the habitat (-.796). A significant correlation between the number of Glyptotendipes barbipes larvae and 1 Rad frequencies (.734) was also discovered (Table XVII). There was no significant correlation between the 1 Rad frequencies and the total number of chironomids, biomass or the index of diversity. TABLE XV Inversion frequencies in chromosome 1 of C. tentans. Samples collected in 1967. From Topping, 1969. Water Body Frequency Frequency Sample of inversion of inversion Size Rad Rade L. Jackson 79.4 20.6 364 L. Greer 81.4 18.6 220 Near Phalarope 77.3 22.7 1168 Near Opposite Crescent 74.3 25.7 214 Barkley L. 74.7 25.3 186 East L. 78.6 21.4 220 Westwick L. 73.6 26.4 1220 Sorenson L. 74.3 25.7 2066 TABLE XVI Summary of correlation coefficients describing the relationship between the frequency of 1 Rad and some environmental factors. With 6 degrees of freedom r = 0.707 is significant at p=.05 and r = 0.834 at p=.01. Con- Org- Total duc- anic nos. Diver• 1 Rad tiv- TDS Na K Ca Mg co3 HC03 Cl S PH Car• ch ir• sity Bio- ity. °4 °2 bon on. Index mass 1 Rad 1.000 Conductivity .411 1.000 T.D.S. .434 .983 1.000 Na .770 .872 .869 1.000 K .668 .766 .713 .914 1.000 Ca -.135 .747 .717 .405 .312 1.000 Mg -.197 .774 .768 .379 .274 .849 1.000 C03 .434 .909 .867 .824 .758 .710 .671 1.000 HCO3 .404 .182 .056 .419 .716 -.092 -.246 .327 1.000 Cl .556 .890 .944 .869 .700 .581 .603 .723 .023 1.000 so4 .196 .899 .936 .653 .434 .792 .895 .764 -.258 .858 1.000 .740 .419 .540 .620 .387 -.068 .082 .251 -.175 .729 .467 1.000 °2 pH -.245 .652 .673 .328 .196 .607 .867 .507 -.313 .493 .780 .109 1.000 Organic -.796 -.104 -.140 -.521 -.585 .465 .394 -.152 -.510 -.316 .120 -.631 .351 1.000 Carbon Total nos. .438 -.102 -.030 .275 .272 -.322 -.482 -.004 .281 .125 -.236 .325 -.277 -.637 1.000 chironomids Index of -.377 -.129 -.259 .295 -.174 .343 .015 .117 .242 -.451 -.217 -.818 -.195 .569 -.319 diversity Biomass .345 -.096 -.005 .149 -.014 -.097 -.410 -.228 -.131 .222 -.092 .389 -.328 -.187 .595 I-1 TABLE XVII Summary of correlation coefficients describing the relationship between the frequency of 1 Rad and the abundance of some chironomids. With 6 degrees of freedom r=0.707 is significant at p=.05 and r=0.834 at p=.01. 1 Rad Derotany- Einfeldia Chironomus Chironomus Chironomus Glyptoten- Procladius Crypto- Rest of pus pagana tentans n.sp. anthraci- dipes (.all chironomus Species alaskensis nus barbipes species) psitta• cinus 1 Rad 1.000 DegPtanypuji 0-415 1.000 alaskensis. / Einfeldia 0.429 0.272 1.000 pagana Chironomus --344 0.194 -0.648 1.000 tentans Chironomus 0-663 0.385 0.332 -0.318 1.000 n.sp Chironomus 0.064 -0.029 0.639 -0.513 -0.071 1.000 anthracinus Glyptotendipes 0.734 0.291 0.674 -0.561 0.428 0.525 1.000 barbipes Procladius 0.329 0.460 0.690 -0.224 -0.051 0.453 0.278 1.000 (all species) Cryptochironomus "0.512 -0.217 -0.743 0.802 -0.438 -0.243 -0.441 -0.595 1.000 psittacinus Rest of species 0.565 0.646 0.425 -0.057 0.156 -0.173 0.475 0.520 -0.456 1.000 Co TABLE XVIII Summary of correlation coefficients describing the relationship between the frequency of 1 Rad and the per cent composition of some chironomids. With 6 degrees of freedom (samples from 8 lakes) r=.707 is significant at p=.05 and r=.834 at p=.01. 1 Rad Derotany- Einfeldia Chironomus Chironomus Chironomus Glyptoten- Procladius Crypto- Remainder pus pagana tentans n.sp. anthraci- dipes (all chironomus of alaskensis nus barbipes species) psitta- Species cinus 1 Rad 1.000 Derotanypus .392 1.000 alaskensis Einfeldia 0.324 -.714 1.000 pagana Chironomus -.556 .837 .828 1.000 tentans Chironomus .564 .041 .262 .100 1.000 n. sp. Chironomus .371 -.672 .109 ,489 -.258 1.000 anthracinus Glyptotendipes .538 .644 .007 -.461 .084 .820 1.000 Barbipes .Procladius .213 -.004 .024 -.226 .501 .333 .085 1.000 (.ail species) Cryptochironomus .570 .790 .648 .863 .016 -.465 -.545 ,273 1.000 psittacinus Remainder -.141 .606 -.161 ,212 -.133 .583 -.549 .428 .333 1.000 cf species h-1 TABLE XIX Summary of the correlation coefficients describing the relationship between the frequency of 1 Rad and some emergence variables. With six degrees of freedom r=0.707 is significant at p=.05 and r=0.834 at p=.01. Variables used are emergence numbers, number of emergence peaks and the time of the main emergence. D. E. £L .C*. G. D. P p « aTask- ten• n. sp. ensis gana tans anth- EITrb- TTnqV- 7^ — £L D. E. C r n nos. nos. nos. nos. no no £aas nos ™ = i . * - no. no — -Cinus jpes peaks peaks peaks p ks - — — «~ tlmc ti» tlme ^ P.alaskpnsJg .561 1.000 numbers E.pagana .299 .553 1.000 numDers ^en^ns -.632 -.335 -.164 1.000 Amber's -5?5 -°97 'S56 -271 1.000 . S^piflua .324 .057 .543 -.168 .911 1.000 Snipes .097 .391 .832 -.238 .210 .188 1.000 ^llgpll^ .535 .788 .481 -.594 .215 .315 .400 1.000 ^fSfrf.peaks ^ ^ ^ -450 -254 -.370 .474 .445 1.000 Sffpeaks -518 -°85 -165 -915 -085 .060 .064 -.304 -.316 1.000 tTo-?em?rg. peaks *173 "-169 -238 -122 -°04 -.050 -.070 .316 -.180 1.000 C.anthracinus -.223 -.032 -.302 -.101 -.048 .324 -.330 .257 -.086 -.026 .436 1. no.ernerg.peaks 000 C.barbipes -.002 .356 -.223 .022 -.399 -.186 -.134 .565 .046 .124 -.124 .455 1.000 no.emerg. peaks • •»-/.» J-.^UU D. alaskensis .362 .167 .148 -.538 .380 .432 .277 .541 .101 -.288 .576 .540 .319 1.000 emerg.time i^rfttme '365 ^ '™ -"° -™ -™ .™ -258 -.863 -.058 .230 .278 .156 1.000 C^f|£f^e -.237 .295 .744 .437 .155 .266 .713 .162 .i09 .727 -.200 -.189 .028 -.002 -.748 1.000 -223 -29? -334 -28? -3°6 '234 -230 .472 -.037 .852 .323 -.098 .701 -.242 .256 1.000 C^agn^s. .021 .135 -.170 -.257 .036 .339 -.246 .589 -.183 -.139 .018 .827 .711 .556 .437 -.177 .013 1.000 fm^ifH -165 -2« -071 -553 -.776 -.120 -.515 .376 -.297 .451 -.221 -.294 -.182 .151 -.413 .166 -.540 1.000 to C. DISCUSSION The stimulus for attempting a study of the biotic interactions influencing C. tentans was Topping's (1969) finding that the frequency of inversions in chromosome 1 was significantly correlated with the number of other chironomids in the environment. Thus the study up to this point has been concerned with the examination of environ• mental influences that might affect C. tentans. Correlation results suggest that C. tentans is par• ticularly successful in Sorenson and Westwick Lakes where oxygen levels are low and organic carbon levels are high. Also associated with these lakes are the drop in larval abundance and the poor emergence of E. pagana and especial• ly G. barbipes. Since oxygen levels, organic carbon and the abundance of G. barbipes correlate with inversion frequency, the chromosome inversion may in some way be connected with these factors. Inversion frequencies are lowest in Sorenson and Westwick Lakes where C. tentans is favoured, suggesting the inversion may control a mechanism reducing competition with G. barbipes in areas where potential interaction is greatest. It was previously noted that the abundances of C. tentans and G. barbipes are correlated in May, but not in FIGURE 29 Seasonal variation in the frequencies of inversions of chromosome 1. Percentages expressed along the ordinate have been converted by arcsin transformation. Samples are from Near Phalarope Lake, 1967. From Topping, 1969. 122 90 i 10 A —i j— 1 1 1 1 1 MAY JUNE JULY AUG. SEPT. OCT. NOV. 123 any subsequent months and it was postulated that during the emergence of overwintering larvae or early in the summer generation a spacing of the peak developmental periods occurred. Figure 29 shows that the fourth instar larvae collected in May had lower inversion frequencies in chromosome 1 than those collected throughout the rest of the summer. The late May emergences of C. tentans are made up from overwintering fourth instar larvae. If these larvae are the ones showing lower inversion frequencies, then subsequent collections of fourth instar larvae would meet with only overwintering larvae and summer generation larvae displaying higher inversion frequencies. If this is so, then the change in inversion frequency between May and June is associated with the initial emergence of C. tentans. It is possible that the portion of overwintering larvae destined to emerge in late May has less tendency to segregate itself (or somehow reduce interaction) from G. barbipes. This behaviour would not be disadvantageous during diapause. In spring and summer, when food and space are at a premium, the inversion frequency is higher and the mechanism reducing interaction would become more important. Thus the mechanism might vary on a temporal as well as a lake basis; whenever the potential competition from G. barbipes is high, the frequency of the inversion 1 Rad is high. Perhaps the inversion in a larva prolongs diapause. There is no real evidence to support this theory, but it fits the postulates outlined above. Clarification of the interactions between C. tentans and other species and of the role of the chromosome inversion is most likely to come from extensive laboratory experiments conducted on controlled populations of the species involved. Monitoring the effects of different species and density mixtures, food levels and light regimes on life cycles and inversion frequencies should enable more definite conclusions to be drawn than were possible in this field study. 125 V CONCLUSION Mundie (1957) in his comprehensive study of the Chironomidae of London reservoirs states, "The study of chironomids can be seen, historically, to have followed two main lines which may be termed the limnological and the entomological. One has been concerned with the dis• tribution of different kinds of chironomids in different lakes, with the association of these with lake types, and with numbers and weights of chironomids as aspects of lake productivity. The other has dealt with the biology of particular species, with their feeding habits, respiration, voltinism, etc. These two lines converge at one point, the central issue in ecology, i.e., the problem of the natural control of populations". The present study has dealt with both of these major lines. The limnological aspects of the work have placed a somewhat different emphasis on chironomid distribution. The different chironomid associations described seem to be determined largely by salinity and associated productivity levels rather than by oxygen concentrations as has been claimed for other lakes (Brundin, 1951). The second avenue of study, the entomological, plays a prominent role in the investigation. A major contribution of the work has been a revision of the distribution of many of the chironomid species under consideration. The fact that 126 this particular insect fauna has been largely neglected in British Columbia is emphasized by the results : eleven species new to B.C., five species new to Canada and seven species new to science (Appendix). One of the main hindrances to advances in ecology is taxonomic ambiguity (Macan, 1963). If underlying taxonomy is confused all ecological discussions and conclusions are necessarily meaningless (Lindeberg, 1967). Great pains were taken to make the best possible identification of the species. The importance of being aware of taxonomic prob• lems in dealing with ecological studies cannot be over• emphasized. Topping (1969) has shown that the same populations of C. tentans examined in this study display differences in the frequency of chromosome inversions. The present thesis suggests that these inversions may regulate a mechanism re• ducing competition between C. tentans and other species, especially G. barbipes. Such a result is in accordance with genetic theory which considers inversions to be adapted to specific ecological conditions (Swanson, 1957; Ford, 1964). Such statements concerning the function of inversions in populations of C. tentans are largely speculative at this time. However, since so little field work has been done on similar problems, any insight at all into the question is of use to ecologically oriented genetics. This work may serve as a basis for further laboratory studies testing the validity of the correlations presented, or studies examining other aspects of the relationship between the chironomid complex and the chromosome inversion frequencies of C. tentans. Although the main objective was to attempt to relate the biology of C. tentans to the biology of coexisting species, the study has thrown some light on the way species life cycles and species composition may differ within a saline lake series. The thesis that a species' life history and population structure may vary radically in closely associated lakes of differing chemical and biological con• stitution has never really been tested in the field before. The phenology of the species often varies considerably from lake to lake even though the lakes may be close together and superficially similar. Differences in species composi• tion and abundance within the same type of habitat are to be expected; environments are never quite the same even when they appear to be. The research, then, emphasizes a basic concept not always appreciated - what is considered a species is capable of much variation in its response to varying environmental conditions. Although the ultimate object of any study of natural communities is a detailed understanding of the organization and interactions of component populations, such an under• taking is too vast for a preliminary study such as this. Mundie (1957) notes that general short term surveys of the chironomid faunas of lakes are likely to prove insufficiently intensive to add much new knowledge. In the present case, however, justification for such a survey (which is as much concerned with defining problems as solving them) rests on the fact that a saline lake series has not been previously studied with chironomids in mind. The thesis was undertaken to add to the knowledge we have of the saline lakes in question, and is a part of a continuing examination of how biological systems function in such environments. 129 LITERATURE CITED Acton, A.B. and G.G.E. Scudder, 1971. The zoogeography and races of Chironomus (Tendipes) tentans Fab. Limnologica 8:83-92. ' Anderson, J.F. and S.W. Hitchcock. 1968. Biology of Chironomus atrella in a tidal cove. Ann. ent. Soc. Am. 1968:1597-16U3~: Anderson, R.O. 1951. A modified flotation technique for sorting bottom faunal samples. Limnol. Oceanogr. 4:223-225. Armitage, P.D. 1968. Some notes on the food of the chironomid larvae of a shallow woodland lake in south Finland. Ann. Zool. Fenn. 5:6-13. Bassett, M. C. 1967. A cytotaxonomic study of the most common larval chironomidae in a series of saline waters in the southern interior of British Columbia. MSc. diss. University of B.C., Vancouver. Bayly, I.A.E. and W. Williams. 1966. Chemical and biological studies on some saline lakes of southeast Australia. Aust.J.mar. Freshwat. Res. 17:177-228. Beadle, L.C. 1943. Osmotic regulation and the faunas of inland waters. Biol. Rev. 18:172-183. Berg, K. 1938. Studies on the bottom animals of Esrom Lake. K. danske Vidensk. Selsk., Naturv. Math. Avd. 9:1-255. Bjerring, J.H. and P. Seagreaves. 1972. UBC TRIP Triangular Regression Package. Univ. of B.C. Computing Centre. Vancouver. Brundin, L. 1949. Chironomiden und andere bodentiere der sudschwedischen urgebirgsseen. Rep. Inst. Freshwat. Res. Drottningholm 30:1-914. Brundin, L. 1951. The relation of 0o microstratification at the mud surface to the ecology of the profundal bottom fauna. Rep. Inst. Freshwat. Res. Drottningholm 32:32-42. 130 Brundin, L. 1958. The bottom faunistical lake type system and its application to the southern hemisphere. Moreover a theory of glacial erosion as a factor of productivity in lakes and oceans. Verh.,int. Ver. Limnol. 13:288-297. Brundin, L. 1966. Transantaretic relationships and their significance as evidenced by chironomid midges with a monograph of the subfamilies Podonominae and Aphroteniinae and the austral Heptagyiae. K. svenska Vetenskskad Handl. 11:1-472. Buck, J.B. 1953. Function of hemoglobin in Chironomus blood. in Roeder, K.D. (ed) Insect Physiology Wiley, N.Y. Buckley, B.R. and J.E. Sublette. 1963. Chironomidae (Diptera) of Louisiana II. The limnology of the upper part of Cane River Lake, Natchitoches Parish, Louisiana, with particular reference to the emergence of chironomidae. Tulane Studies in Zoology 11:151-166. Cannings, R.A. 1970. Chironomidae and fish predation in Westwick Lake. BSc. diss. Univ. of B.C., Vancouver Cannings, R.A. 1972. An emergence trap for aquatic insects. Vancouver Natural History Society Discovery 1 (2):48-53. Clark, K.J. 1971. Effects of photoperiod on the larval development of Chironomus tentans. BSc. diss. Univ. of B.C., Vancouver. Corbet, P.S. 1964. Temporal patterns of emergence in aquatic insects. Can. Ent. 96:264-279. Corbet, P.S. 1965. An insect emergence trap for quantitative studies in shallow ponds. Can. Ent. 97:845-848. Davis, J.T. 1960. Fish populations and aquatic conditions in polluted waters in Louisiana. La. Wildlife and Fish. Comm. Bull. 5:1-121. DeBach, P. 1966. The competitive displacement and coexist• ence principles. Ann. Rev. Ent. 11:183-212. Decksbach, N.K. 1924. Seen und Flusse des Turgai - Gebietes (Kirgisen-Steppen). Verh. int. Ver. Limnol. 2:252-288. Deevy, E.S. 1942. The biostratonomy of Linsley Pond. Amer. J. Sci. 240:264-283; 313-324. 131 Edwards, F.W. 1929. British non-biting midges. Trans• ent. Soc. Lond. 77:279-430. Elton, C. 1946. Competition and the structure of ecological communities. J. Anim. Ecol. 15(l):54-68. Englemann, W. and D.G. Shappirio. 1965. Photoperiodic control of the maintenance and termination of larval diapause in Chironomus tentans. Nature 207: 548-549. Fagan, E. and W.R. Enns. 1966. The distribution of aquatic midges in Missouri Lagoons. Proc. Entomol. Soc. Wash. 68:277-289. Ford, E.B. 1964. Ecological Genetics. Methuen and Co. London. Gerry, B.I. 1951. Some mosquito-like nuisance pests and their economic significance. Mosquito News 11:141-144. Gibbs, K.E. 1971. Observations on the biology and seasonal distribution of some Ephemeroptera in a stream system at Rigaud, Quebec. PhD. diss. Univ. McGill. Montreal. Goulden, C.E. 1964. Progressive changes in the cladoceran and midge fauna during the ontogeny of Esthwaite Water. Verh. int. Ver. Limnol. 15:1000-1005. Hall, D.J., W.E. Cooper and E.E. Werner. 1970. An experimental approach to the production dynamics and structure of freshwater animal communities. Limnol. Oceanogr. 15:839-928. Hamilton, A.L. 1965. An analysis of a freshwater benthic community with special reference to the Chironomidae. PhD. diss. Univ. of B.C., Vancouver. Hardin, G. 1960. The competitive exclusion principle. Science 131:1292-1298. Harnish, 0. 1960. Untersuchungen am 0£ - Verbrauch der larven von Chironomus anthracinus and Chironomus plumosus. Arch. Hydrobiol" 57:179-186. Harp, G.L. and R.S. Campbell. 1967. The distribution of Tendipes plumosus (Linne) in mineral acid water. Limnol. Oceanogr. 12:260-263. Hilsenhoff, W.L. 1966. The biology of Chironomus plumosus (Diptera: Chironomidae) in Lake Winnebago, Wisconsin. Ann. Entom. Soc. Amer. 59:465-473. 132 Humphries, CF. 1936. An investigation of the profundal and sublittoral fauna of Windermere. J. Anim. Ecol. 5:29-52. Hutchinson, G.E. 1957. Concluding remarks. Cold Spring Harbor Symp. Quant. Biol. 22:415-427. Hutchinson, G.E., G.E. Pickford and J.F.M. Schuurman. 1932. A contribution to the hydrobiology of pans and other inland waters of South Africa. Arch. Hydrobiol. 24:1-154. Ide, F.P. 1935. The effect of temperature on the distribu• tion of the mayfly fauna of a stream. Univ. Toronto Stud, biol. 39:1-76. lilies, J. 1952. Die Plecopteren und das Monardische Prinzip. Ber. Limnol. Flusst. Freudenthal 3:53-69. Jansson, A. and G.G.E. Scudder. 1973. The life cycle and sexual development of Cenocorixa species (Hemiptera: Corixidae) in the Pacific Northwest. Ms. Univ. of B.C. Jenner, C.E. 1958. The effect of photoperiod on the duration of nymphal development in several species of Odonata. Quart. Pubn. Ass. S. Biol. Philadelphia. 6:26. Johnson, M.G. and R.O. Brinkhurst. 1971. Associations and species diversity in Benthic macroinvertebrates of Bay of Quinte and Lake Ontario. J. Fish. Res. Bd. Canada 28:1683-1697. Jonasson, P.M. 1954. An improved funnel trap for capturing emerging aquatic insects, with some preliminary results. Oikos 5 :179-188. Jonasson, P.M. 1955. The efficiency of sieving techniques for sampling freshwater bottom fauna. Oikos 6:183-207. Judd, W.W. 1953. A study of the population of insects emerging as adults from the Dundas Marsh, Hamilton, Ontario, during 1948. Amer. Midi. Nat. 49:801-824. Judd, W.W. 1957. A study of the population of emerging and littoral insects trapped as adults from tributary waters of the Thames River at London, Ontario. Amer. Midi. Nat. 63:194-210. Judd, W.W. 1961. Studies of the Byron Bog in southwestern Ontario. XII. A study of the population of insects emerging as adults from Redmond's Pond in 1957. Amer. Midi. Nat. 65:89-100. 133 Kajak, Z. , K. Dusoge and A. Stanczykowska. 1968. Influence of mutual relations of organisms, especially Chironomidae, in natural benthic communities, on their abundance. Ann. Zool. Fenn. 5:49-56. Khinchin, A.I. 1957. Mathematical foundations of informa• tion theory. Dover Publications. New York Kimerle, R.A. and N.H. Anderson. 1971. Production and bioenergetic role of the midge Glyptotendipes barbipes (Staeger) in a waste stabilization lagoon. Limnol. Oceanogr. 16:646-659. Koskinen, R. 1968. Seasonal and diel emergence of Chironomus salinarus Kieff. (Diptera: Chironomidae) near Bergen, Western Norway. Ann. Zool. Fenn. 5:65-70. Larkin, P.A., P.J. Ellickson and D. Lauriente. 1970. The effects of Toxaphene on the fauna of Paul Lake, British Columbia. Fisheries Management Pub. 14:1-28. B.C. Fish and Wildlife Branch. Lauer, G.J. 1969. Osmotic regulation of Tanypus nubifer, Chironomus plumosus and Enallagma clausum in various concentrations of saline lake water. Physiol. Zool. 42:381-387. Leathers, A.L. 1922. Ecological study of aquatic midges and some related insects with special reference to feeding habits. Bull. Bur. Fish. Wash. 38:1-61. . Lellak, J. 1965. The food supply as a factor regulating the population dynamics of bottom animals. Mitt, int. Ver. Limnol. 13:128-138. Lenz, F. 1925. Chironomiden und Seentypenlehre. Naturwissenschaften 13:5-10. Lindeberg, B. 1967. Sibling species delimitation in the Tanytarsus lestagei aggregate (Diptera: Chironomidae). Ann. Zool. Fenn. 4:45-86. Lindeberg, B. 1968. Population differences in Tanytarsus gracilentus (Holmgr.) (Diptera: Chironomidae). Ann. Zool. Fenn. 5:88-91. Lundbeck, J. 1926. Die bodentierwelt norddeutscher Seen. Arch. Hydrobiol. Suppl. 7:1-473. Macan, T.T. 1963. Freshwater Ecology. Longmans, Green and Co. London. 134 MacArthur, R.H. 1965. Patterns of species diversity. Biol. Rev. 40:510-533. MacArthur, R.H. and J.W. MacArthur. 1961. On bird species diversity. Ecology 42:594-598. McAlpine, J.F. 1964. Arthropods of the bleakest barren lands: composition and distribution of the arthropod fauna of the northwestern Queen Elizabeth Island. Can. Ent. 96:127-129. Malloch, J.R. 1915. The Chironomidae, or midges, of Illinois, with particular reference to the species occurring in the Illinois River. 111. State Lab. Nat. Hist. Bui. 10:275-543. Margalef, R. 1968. Perspectives in ecological theory. Univ. Chicago Press. Chicago. Miller, R.B. 1941. A contribution to the ecology of the Chironomidae of Costello Lake, Algonquin Park, Ontario. No. 49. Pub, of Ont. Fisheries Res. Board. LX. Univ. Toronto Studies Biol. Series^ Munro, J.A. 1941. Studies of waterfowl in British Columbia. The Grebes. Occasional papers of the British Columbia Provincial Museum 3 :1-71. Munro, J.A. 1945. The birds of the Cariboo Parklands, British Columbia. Can. J. Res. 23:17-103. Munro, J.A. and I. McT. Cowan. 1947. A review of the bird fauna of British Columbia. Spec. Publ. Br. Columb. Prov. Mus. 2:1-285. Morgan, N.C. and A.B. Waddell. 1961. Diurnal variation in the emergence of some aquatic insects. Trans, ent. Soc. Lond. 113:123-137. Morrissey, T. 1950. Tanypodinae of Iowa (Diptera) III Amer. Midi. Nat. 43:88-91 Mundie, J.H. 1956. Emergence traps for aquatic insects. Mitt, int. Ver. Limnol. 7:1-13. Mundie, J.H. 1957. The ecology of Chironomidae in storage reservoirs. Trans. R. ent. Soc. Lond. 109:149-232. Northcote, T.G. and P.A. Larkin. 1956. Indices of productivity in British Columbia Lakes. J. Fish. Res. Bd. Canada. 13:515-540. 135 Oliver, D.R. 1963. Entomological studies in the Lake Hazen area, Ellesmere Island, including lists of species of Arachnida, Collembola and Insecta. Arctic 16:175-180. Oliver, D.R. 1964. A limnological investigation of a large arctic lake, Nettilling Lake, Baffin Island. Arctic 17:69-83. Oliver, D.R. 1968. Adaptations of arctic Chironomidae. Ann. Zool. Fenn. 5:111-118. Oliver, D.R. 1971. Life History of the Chironomidae. Ann. Rev. Ent. 16:211-230. Oliver, D.R. 1971 B. Description of Einfeldia synchrona n.sp. (Diptera: Chironomidae). Can. EntH 103 :1591-1595. Paine, G.H. and A.F. Gaufin. 1956. Aquatic diptera as indicators of pollution in a midwestern stream. Ohio J. Sci. 56 (5) :291-304. Palmen, E. 1962. Studies on the ecology and phenology of the chironomids of the northern Baltic. Ann. Ent. Fenn. 28:137. Palmen, E. and L. Aho. 1966. Studies on the ecology and phenology of the Chironomidae (Diptera) of the northern Baltic. 2. Camptochironomus Kieff. and Chironomus Mieg. Ann. Zool. Fenn. 3:217-244. Pask, W.M. and R.R. Costa. 1971. Efficiency of sucrose flotation in recovering insect larvae from benthic stream samples. Can. Ent. 103: 1649-1652. Pater son, C.G. and CH. Fernando. 1971. Studies on the spatial heterogeneity of shallow water benthos with particular reference to the Chironomidae. Can. J. Zool. 49:1013-1019. Petr, T. 1971. Establishment of chironomids in a large tropical man-made lake. Can. Ent. 103:380-385. Phillips, J.E. and J. Meredith. 1969. Active sodium and chloride transport by anal papillae of a salt water mosquito larva (Aedes campestris) Nature 222:168-169. Rawson, D.S. and J.E. Moore. 1944. The saline lakes of Saskatchewan. Canad. J. Res. (D) 22:141-201. Remmert, H. 1955. Okologische untersuchungen uber die dipteren der Nord und Ostsee. Arch. Hydrobiol. 51:2-53. 136 Roback, S.S. 1969. Notes on the food of Tanypodinae (Diptera: Chironomidae). Ent. News 80:13-18. Roback, S.S. 1971. The adults of the subfamily Tanypodinae (=Pelopinae) in North America. Monogr. Acad. Nat. Sci. Philad. 17:1-410. Sadler, W.O. 1935. Biology of the midge Chironomus tentans Fabricius and methods for its propagation. Cornell.U. Agri. Exp. Station Mem. 173:1-25. Saether, O.A. 1967. Notes on the bottom fauna of two small lakes in northern Norway. Nytt. Mag. Zool. 14:96-124. Saether, O.A. 1969. Some Nearctic Podonominae, Diamesinae and other Orthocladiinae (Diptera: Chironomidae). Bull. Fish. Res. Bd. Canada. 170:1-154. Salt, G. and F.J.S. Hollick. 1944. Studies on wireworm populations. I. A census of wireworms in pasture. Am. Appl. Biol. 31:52-64. Sandberg, G. 1969. A quantitative study of chironomid distribution and emergence in Lake Erken. Arch. Hydrobiol. Suppl. 35:119-201. Schlee, D. 1966. Praparation und Ermittlung von Messwerten an Chironomidae (Diptera). Gewasser Abwasser 41:169-193. Scudder, G.G.E. 1969 A. The fauna of saline lakes on the Fraser Plateau in British Columbia. Verh. int. Ver. Limnol. 17:430-439. Scudder, G.G.E. 1969 B. The distribution of two species of Cenocorixa in inland saline lakes of British Columbia. J. Entomol. Soc. Brit. Columbia 66:32-41. Scudder, G.G.E. and K.H. Mann. 1968. The leeches of some lakes in the southern interior plateau region of British Columbia. Syesis 1:203-209. Scudder, G.G.E., M.S. Jarial and S.K. Choy. 1972. Osmotic and ionic balance in two species of Cenocorixa (Hemiptera). J. Insect,Physiol. 18:883-895. Siegel, S. 1956. Nonparametric statistics for the behavioral sciences. McGraw-Hill. New York. Stahl, J.B. 1969. The uses of chironomids and other midges in interpreting lake histories. Mitt, int. Ver. Limnol. 17:111-125. 137 Stone, A., C.W. Sabrosky, W.W. Wirth, R.H. Foote and J.R. Coulson. 1965. A catalog of the Diptera of America north of Mexico. U.S. Dept. Agr. Handbook 276 :1-1696. Sturgess, B.T. and R.L. Goulding. 1968. Tolerance of three species of larval Chironomidae to physico-chemical stress factors occurring in stabilization lagoons. Ann, ent. Soc. Amer. 61:903. Sturgess, B.T. and R.L. Goulding. 1969. Abundance and microdistribution of larval Chironomidae in stabiliza• tion lagoons. Ann, ent. Soc. Amer. 62:97. Sublette, J.E. 1957. The ecology of the macroscopic bottom fauna in Lake Texoma (Denison Reservoir), Oklahoma and Texas. Amer. Midi. Nat. 57:371-402. Sublette, J.E. 1960. Chironomid midges of California I.Chironomidae exclusive of Tanytarsini. Proc. U.S. Nat. Mus. 112:197-226. Sublette, J.E. 1963. Chironomidae (Diptera) of Louisiana. I. Systematics and immature stages of some lentic chironomids of west-central Louisiana. Tulane Studies in Zoology 11:109-150. Sublette, J.E. 1964. Chironomid midges of California II. Tanypodinae, Podonominae and Diamesinae. Proc. U.S. Nat. Mus. 115 :85-135. Sublette, J.E. 1967. Type specimens of Chironomidae (Diptera) in the Cornell University collection. Journal of the Kansas Entomological Society 40:477-564. Sublette, J.E. 1970. Type specimens of Chironomidae (Diptera) in the Illinois Natural History Survey collection, Urbana. Journal of the Kansas Entomological Society 43:44-95. Sublette, J.E. and J.S. Dendy. 1959. The use of transparent plastic material for the construction of simplified tent and funnel traps. S.W. Nat. 3:220-223. Sublette, J.E. and M.S. Sublette. 1965. Family Chironomidae (Tendipedidae) in Stone et al (ed) A Catalog of the Diptera of America north of Mexico. U.S. Dept. Agr^ Handbook 276:1-1696. Sutcliffe, D.W. 1960. Osmotic regulation in the larvae of some euryhaline Diptera. Nature 187:331. 138 Suworow, E.K. 1908. Zur Beurteilung der lebenserscheinungen in gestatigten salzseen. Zool. Anz. 32:647-674. Swanson, CP. 1957. Cytology and Cytogenetics. Prentice Hall. Englewood Cliffs. N.J. Thienemann, A. 1920. Biologische Seetypen und die Grundung ainer hydrobiologischen Anstalt am Bodensee. Arch. Hydrobiol. 13:347-370. Thienemann, A. 1951. Das Schwarmen von Chironomus bathophilus Kieff. (=anthracinus Zett.) im Ploner Seengebiet, 1918-50. Arch. Hydrobiol. Suppl. 18:692-704. Topping, M.S. 1969. Giant chromosomes, ecology and adaptation in Chironomus tentans• PhD. diss. University of B.C., Vancouver. Topping, M.S. 1971. Ecology of larvae of Chironomus tentans (Diptera: Chironomidae) in saline lakes in central British Columbia. Can. Ent. 103:328-338. Topping, M.S. 1972. The distribution of Chironomus tentans in some lakes in central British Columbia in relation to some physical and chemical factors. Proc. XIII int. Congr. Ent. 3:477-478. Townes, H.K. 1945. The Nearctic species of Tendipedini. Amer. Midi. Nat. 34:1-206. Walshe, B.M. 1947 A. On the function of hemoglobin in Chironomus after oxygen lack. J. exp. Biol. 24:329. Walshe, B.M. 1947 B. The function of hemoglobin in Tanytarsus (Chironomidae) J. exp. Biol. 24:343-351. Walshe, B.M. 1950. The function of hemoglobin in Chironomus plumosus under natural conditons. J. exp. Biol. 27 :73-95. Wigglesworth, V.B. 1933. The adaptation of mosquito larvae to salt water. J. exp. Biol. 10:27-37. Williams, W.D. 1966. Conductivity and concentration of total dissolved solids in Australian lakes. Aust. J. mar. Freshwat. Res. 17:169-176. Wohlshlag, D.E. 1950. Vegetation and invertebrate life in a marl lake. Invest. Indiana Lakes and Streams 3 (9):321-372. 139 Wulker, W. 1956. Zur Kenntnis des Gattung Psectrocladius Kieff. Diptera: Chironomidae). Arch. Hydrobiol. Suppl. 24:1-66. Wurtz, C.B. and S.S. Roback. 1955. The invertebrate fauna of some Gulf Coast rivers. Proc. Acad. Nat. Sci. Phila. 107:167-206. APPENDIX Species Identified in the Study * New records for British Columbia ** New records for Canada *** Species new to science FAMILY CHIRONOMIDAE SUBFAMILY TANYPODINAE Tribe Tanypodini Tanypus punctipennis Meigen Tribe Macropelopiini Subtribe Macropelopiina Derotanypus alaskensis (Malloch)* Derotanypus n.sp.*** Subtribe Procladiina Procladius (Psilotanypus) bellus (Loew) Procladius (Psilotanypus) nietus Roback Procladius freemani Sublette Procladius ruris Roback Procladius dentus Roback * Procladius clavus Roback * Procladius sublettei Roback Procladius n.sp. *** Tribe Pentaneurini Ablabesmyia peleensis (Whalley) * SUBFAMILY ORTHOCLADIINAE Tribe Orthocladiini Nanocladius n.sp. *** Cricotopus albanus Curran * Cricotopus flavibasis Malloch ** Cricotopus trifasciatus (Panzer) * Acricotopus nitidellus Malloch ** Psectrocladius barbimanus (Edwards) * Psectrocladius zetterstedti Brundin ** Psectrocladius n.sp. *** SUBFAMILY CHIRONOMINAE Tribe Chironomini Chironomus anthracinus Zetterstedt Chironomus atrella (Townes) * Chironomus tentans Fabricius Chironomus plumosus (Linnaeus) Chironomus n.sp. (near atritibia) *** Chironomus n.sp. *** Einfeldia pagana Meigen * Cryptochironomus psittacinus Meigen * Cryptotendipes ariel (Sublette) ** 142 Endochironomus nigricans Johannsen Glyptotendipes barbipes (Staeger) Polypedilum n.sp. *** Tribe Tanytarsini Calopsectra gracilenta (Holmgren) * Calopsectra holochlorus (Edwards) **