AN ABSTRACT OF THE THESIS OF.

Brian Thornas Sturgess for the M. S. in Entornology (Narne) (Degree) (Major)

Date theeis is presented Septernber 4, 19 64

Title The Ecology of Associated with Waste Water Lagoons Redacted for Privacy Abstract approved Profe s

The purpose of this study was to deterrnine what species occurred in waste water facilities at Corvallis, Oregon, and to correlate these species with the chernical, physical, and biological features comrnon to these facilities. Data collected on a routine basis included dissolved oxygen, ternperature, algal density, and insect population sarnples. Most of this work was conducted during

L963-64 at an experirnental waste water lagoon that received rnunici- pal sewage from Corvallis. Observations were also rnade at an agri- cultural waste water lagoon that received wastes frorn a hog farrn located at Oregon State University. Insect larvae were collected with an aquatic dip net and a six inch square Eckrnan dredge.

Adults were collected in a floating trap.

Environrnental conditions for insects occurring in the experi- mental waste water lagoon fluctuated rapidly at tirnes. This was due to shock loadings of influent containing high arnounts of biochernical oxidation demand. \4rhen these variations in environ- mental conditions are considered, any insect population occurring in the lagoon rnust be either tolerant to these fluctuations, seasonal residents, or transitory residents. All the insect species confined their activities to the peripheral portions of the lagoon. Eight spe- ciee of the Herniptera were recovered; and of these Notonectidae and Corixidae were the most numerous. Dytiscidae and Hydrophili- dae were the rnost important Coleoptera. Representatives of Dip.. tera were the most abundant species. Larval Culicidae were seasonally abundant. Psychodidae and Syrphidae were infrequent in occurrence.

The larval populations of the farnily Chironornidae were the rnost dorninant feature of the lagoon. Procladius sp. and Chironornus sp. were perrlanent residents and were lirnited in their rnicro- distribution to an ar€a 0. 6 feet to 2.6 f.eet deep and two to seven feet frorn the shore. No insects were recovered frorn the central areas of the Lagoon. The rnain chernical and physical factors affecting the insect populations in the lagoon are, influent quality and quantity, wave action, bottorn sedirnents, and clirnatic conditions. Arnong the biological rnechanisrns affecting the insect populations are algal photosynthesis, peripheral vegetation, and insect predator-prey relationships. THE ECOLOGY OF INSECTS ASSOCIATED WITH WASTE WATER LAGOONS

by

BRIAN THOMAS STURGESS

A THESIS

submitted to

OREGON STATE UNIVERSITY

in partial fulfillrnent of the requirements for the degree of

MASTER OF SCIENCE

Septernber, L964 APPROVED: Redacted for Privacy

Profes sor of Entornology

In Charge of Major Redacted for Privacy

Chairman, Departrnent of Entornology Redacted for Privacy

Graduate School

Date thcsis is preeented Septernber 4, 1964

Typed by I:ctty Hoetetter ACKNOWLEDGMENTS

I wish to express rny sincere appreciation to the following per- sons for their assistance during the course of study and preparation of this thesis:

To rny rnajor professor, Dr. R. L. Goulding, for his guidarice during this study and for his assistance in the writing of the rnanu- s c ript.

To Dr. P. O. Ritcher, Chairrnan, Department of Entornology, and Dr. N. H. Anderson for the critical reading of the rnanuscripi;.

To the many staff rnernbers of the Civil Engineering Depart- rnent. In particular I thank Dr. M.E. Northcraft for the use of equiprnent and laboratory facilities.

To the following specialists for identifications of aquatic in- sects: Dr. J. D. Lattin (Herniptera), Dr. J.E. Sublette (Chironorni- dae) and Dr. F. C. Harrnston ().

And finally to rny wife Rornana for her assistance, understand- ing, and patience. TABLE OF CONTENTS Page INTRODUCTION t

MATERIALS AND METHODS

Procedures for obtaining chernical sarnples 4 Procedures for obtaining physical sarnples . 5 Procedures for obtaining biological sarnples 6 Laboratory procedures for insect rearing B Description of waste stabilization facilities q

PHYSICAL AND CHEMICAL FINDINGS . 13 Influentquality . t3 Dissolved oxygen relationships . 15 Sludge deposition . i9 Chernical observations at farrn stabitization pond . . Z0

BIOLOGICAL RESULTS . z6

Order Odonata Z9 Order Herniptera Z9 Order Coleoptera . 30 Order Diptera. 3l LaboratoryObservations. . .38 Observations at a farrn stabilization pond . 4L

DISCUSSION

SUMMARY 54

BIBLIOGRAPHY . 56 LtrST OF TABLES

Table _Prg" Dissolved oxygen deterrninations, ternperature readings, and algal sarnples. Experirnental waste water lagoon, Corvallis, Oregon. . .I4 2 Diurnal variation in dissolved oxygen content at the surface of the secondary celI, February 28, 1964. . l8 3 Dissolved oxygen gradient in pprn to water depth and distance frorn the shore. South transect, waste water lagoon, 2 P. M., February 28, L964. . lB 4 Variation in deptJr of core sarnples of bottorn sludge to water depth in feet. Waste water lagoon, February 28, 1964 . ,2r 5 Insects recovered frorn the experirnental waste stabilization lagoon at Corvallis, Oregon . 27 5 Nurnbers of larval Chironornidae recovered by 5 inch square dredge sarnples. North transect, prirnary cel1, waste water lagoon, August 2, L963 . . 33 7 Nurnbers of larval Chironornidae recovered by 6 inch s(Iuare dredge sarnples. East transect, secondary ceIl, waste water lagoon, Corvallis, August 5, 1963 . 34 8 Nurnbers of larva1 Chironornidae recovered by 6 inch square dredge sarnples. South transect, secondary cel1, waste water lagoon, Corvallis, August !, 1963 . 34 9 Nurnbers of larval Chironornidae recovered by 6 inch square dredge sarnples. North transect, prirnary cell, waste water lagoon, Corvallis, February 6, L964 . 36 I0 Nurnbers of larval Chironornidae recovered by 6 inch square dredge sarnples. East transect, secondary cell, waste water lagoon, Corvallis, February 7, 1964. . 36 1l Nurnbers of larval Chironornidae recovered by 6 inch sguare dredge sarnples. South transect, secondary ceIl, waste water lagoon, Corvallis, February 10, 1964 . 37 LIST OF F'IGURES

Figure Page

I Six inch square Eckrnan dredge used to obtain larval Chironornidae frorn the bottorn of the lagoon 7

?, Floating pyrarnidal ernergence trap used to trap adult Chironom idae as they ernerged frorn the water . 7 3 Experirne ntal waste water lagoon plan. Corvallis, Oregon 10

4 East ce1l of the waste water lagoon showing grass growing along the periphery of the lagoon . l l 5 Agricultural waste water lagoon at the hog farrn. Oregon State University . l l 6 Old ox-bow of Oak Creek showing the result of effluent frorn the agricultural waste water lagoon. . lZ

7 Core sarnples frorn the north transect showing an increase of sludge deposition rate to depth . . ZZ

8 Core sarnples frorn the east transect showing an increase of sludge deposition rate to depth . . Zz

9 Core sarnples of the south transect showing an increase of sludge depositj.on rate to depth . . . 23

I0 Dissolved oxygen deterrninations of sarnples taken frorn the secondary cell , experirnental waste water lagoon, Corvallis, Oregon . . .25

I I Ternporal distribution of insect farnilies occurring at the experirnental waste water lagoon z8 THE ECOLOGY OF INSECTS ASSOCIATED WITH WASTE WATER LAGOONS

INTRODUCTION

The following is a study of insects naturally occurring in ex- perirnental waste water lagoon at the City of Corvallis, and also in- cludes observations of insects and their environrnental conditions in a farrn stabilization pond located at the hog farrn of the Oregon State

University Agricultural Experirnent Station, Corvallis. Observa- tions began in June 1963 and a wide variety of environrnental changes, and attendant consequences to the insect populations under study, were recorded before the terrnination of this work in March, 1964.

The purpose of this study was to deterrnine what insect popula- tions occurred in the waste water facilities being studied, and to correlate the insect population structure with the physical and cherni- cal conditions found in these facilities.

As our rnodern society continues to expand, waste water dis- posal problerns also expand. Waste water disposal by conventional treatrnent plants is becorning rnore expensive to operate and rnain- tain, Many smaller cornrnunities and industrial rnanufacturing plants cannot afford this increase in cost of waste water treatrnent.

One answer to the high cost of waste water treatrnent is the waste water lagoon. These waste water lagoons can be built for about $4.-50 to $20.00 per capita, or about one eighth to one half the cost of a conventional plant (5, p, 771,

Several general descriptions of the use of waste water lagoons and the rnechanisrn of sewage treatrnent are published (4, 9, 1I, 27, and 32). In this mechanisrn bacteria and unicellular algae play the principal role of stabilizing decornposable organic rnaterials.

Microbial decornposition of unstable organic matter is usually oxidation carried out by saprophytic organisrns. These organisrns use the organic rnaterial as a source of energy in their rnetabolism.

Factors affecting the degree of stabilization are the nature of the organic rnaterial and the availability of dissolved oxygen, Oxidative biochemical reactions are aerobic bacteria utilizing dissolved oxy- gen are cornplete. They produce carbon dioxide and water as end products and yield a rnaximurn of energy.

Oxidation by anaerobic bacteria is incornplete, as far as sta- bilization is concerned, and produces less energy for these organisrns,

In addition to carbon dioxide and water, anaerobic bacteria also pro- duce incompletely oxidized products such as hydrogen sulfide,rnethane, alcohols, ketones and organic acids (9), These products are sus- ceptible to eventual cornplete oxidation by the sarne or higher organ- isrns in the presence of oxygen.

Only aerobic bacteria are able to carry out cornplete oxidation, and they are essential for the stabilization of decornposable organic rnatter in waste water lagoons, As rnore stable products are pro-

duced by the biochernical reactions of bacteria, single-celled algae use these products as nutrients needed for their growth and repro- duction. In turn, the alga1 suspension wiII produce dissolved oxygen by photosynthesis.

If algal photosynthesis produces a sustained yield of dissolved oxygen during the hours of sunlight, aerobic conditions can be rnain- tained in waste water lagoons. However, if dissolved oxygen is not produced in sufficient arnounts to keep up with the dernands of the stabilization rnechanisrn, anaerobic conditions will prevail and noxious gases will be produced.

All factors affecting the stabilization processes should be studied if the desired reduction of biochernical oxygen demanding substances in waste water lagoons is to be fully understood. 'Work by Usinger and Kellan (28, p. 285) has shown that insects have a definite role in rernoving oxygen dernanding substances frorn waste water lagoons.

Dissolved oxygen content is the prirnary factor in the rnicro- distribution, and the species composition of insect populatiors oc- curring in these waste water facilities, As sarnpling technique would differ for each species encountered, very little quantitative work was carried out in this study, and in order to confine the scope of these observations within the prirnary purpose, observations on rnany species were necessarily qualitative in approach. 4

MATERIA],S AND METHODS

To better understand the relationship of insect populations to their environrnent, physical and chernical data were collected as well as the insect species involved. Most of the chernical data was taken from a boat dock in each cell. A ten foot boat was used to ob- tain sarnples of bottorn insect fauna and sludge sarnples.

Procedures for Obtaining Chernical Sarnples

'Water samples for analysis were collected in ground glass- stoppered biochernical oxidation dernand (BOD) bottles of 300 rnl. capacity. Two sarnpling bottles were placed in a plastic rnodification of the dissolved oxygen and biochemical oxygen dernand sarnpler de- veloped by the Arnerican Pub1ic Health Association (I, p. ZsL),

This sarnpler enables water to be siphoned frorn below the water level by displacing air frorn the BOD bottle volurne several tirnes.

This prevents aerated water frorn being sarnpled during the process.

Routine sarnples were taken at the boat dock six inches below the water surface and six inches above the sludge-water interface and due to the limitations of sarnpling rnethod used, served as the ,top and bottomtr sarnples.

Dissolved oxygen was deterrnined by the unrnodified winkler rnethod (I, p. z5zl, rrfixedrr in the field and titrated for dissolved oxygen in the laboratory.

The basic procedure entails the oxidation of rnanganous hy- droxide in a highly alkaline solution. Upon acidification in the pres- ence of an iodide, the rnanganic hydroxide dissolves and free iodine is liberated in an arnount equivalent to the oxygen originally dissolved in the sarnple. The free iodine is titrated with a standard sodiurn thiosulfate solution, using starch as an internal indicator after the iodine has been reduced. The norrnality of the thiosulfate solution is adjusted so that one rnI. is equivalent to one rnl. per liter of dis- solved oxygen when 200 rnl. of the original sarnple is titrated. Dis- solved oxygen in rng. per liter is equivalent to dissolved oxygen in parts per rnillion. The dissolved oxygen was then recorded as parts per rnillion.

Procedures for Collecting Physical Sarnples

Plastic tubes of I.75 inches inside diarneter by one foot in length were used to obtain sludge depth sarnples. After attaching a six foot alurninum tube as a handle, sarnples were obtained by driv- ing the one foot plastic tube through the sludge blanket until the bottorn end of the tube becarne plugged with bottom clay. The clay plug enabled the sarnple to be brought to the surface without loss. The sample tube was disconnected frorn the aluminurn extension and sealed with a nurnber seven stopper at each end. 6

Procedures for Obtaining Biological Samples

Algal sarnples were collected in the Bame manner as dissolved oxygen sarnples. The algal cell volume was obtained by centrifuging

100 rnls. of the sarnple at 300 revolutions per rninute. CelI volurne was then recorded as mIs. of algae per 100 rnls. of water.

Most of the insect collecting was done with an aquatic dip net either frorn the bank or frorn a boat. Specimens collected were transferred into jars of 70 percent alcohol and later identified in the laboratory, Some samples were placed in one gallon jars in water from their natural habitat and brought back to the laboratory for ob- servation. Orrantitative samples of the bottorn fauna were taken with a six inch square Eckrnan dredge, Figure l. Each bottorn sarnple was placed in a five gallon plastic bucket to facilitate screening.

The screens used were Tyler standard screens of nine and 32 rnesh- es per inch. The larger debris was rernoved by the coarse screen and the larvae were then hand picked frorn the 3? rnesh screen. The insects were recovered by placing a srnall portion of the bottorn sedirnents at a tirne in sieves, flushing away the excess rnaterial by agitating the sieves in the water at the side of the boat. This process was repeated until all larvae were recovered frorn the sarnple. The larvae were then placed in nurnbered vials of 70 percent alcohol to be counted and recorded. Figure t . Six iach square Eckman dredge used to obtain larval Chironornidae frorn the bottorn' of the Lagoon.

Eijure 2 . Floating pyrarnidal emergence trap ueed to trap adult Chirorlornidae as they ernerged from the water. 8

A floating pyrarnidal trap, Figure 2, was used to collect adults as they ernerged frorn the pupal stage at the surface of the water.

The base of the trap was 2.5 feet square. Frarnework was construct- ed of one inch square pine wood and covered with black broadcloth.

Four tubular floats were attached to the base of the trap. A quart jar with an inverted clear plastic cone, Figure 2, was fitted to the top, To collect adults, a duplicate jar and cone assembly was changed for the one on the pyrarnid trap, and taken to the laboratory for the identification and counting of specirnens.

In Septernber it becarne necessary to control mosquito breed- ing in the lagoon. A larvicide solution of five percent Malathion in diesel oil was mixed, This was applied with a one gallon spray can at the rate of 0,5 gallon per acre.

Laboratory Procedures for Insect Rearing

Insects were reared in one gallon glass jars witl. holes cut in the lids to accomrnodate glass larnp chirnneys fitted with inverted plastic cones. Insects ernerging frorn the water contained in the jars were then recovered frorn the glass larnp chirnneys.

More detailed observations of larval Chironornidae were car- ried out in petri dishes. Stabilized aquariurn debris was placed in the dishes and the presence of abundant srnall Crustacea, principally

Cyclops sp., served as indicators of aerobic conditions. The absence of hydrogen sulfide and arnrnonia production, also indicated aerobic conditions in the dishes. Larval Chironornidae collected in the field were used for laboratory observations. The largest larval sizes were used and as no interstadial exuvia were found in the dish-

€s, these were presumably the last larval instar.

Water in the one gallon jars was aerated by pressure forced through aeration stones, Air pressure for aeration was provided by an Oscar electric vibrator purnp, Insects were identified to species where possible. Slides of the family Chironornidae were sent to Dr.

J. E. Sublette, Eastern New Mexico University, Portales, New Mex- ico, but they have not been deterrnined to species at this tirne.

Description of.Waste Stabilization Facilities

The experirnental waste water lagoon was located 600 feet north of the Corvallis Sewage Treatment P1ant, The facility con- sisted of two cells, each I.07 acres in surface area (Figure 3).

Dikes enclosing the unit were eight feet in width at the top. These dikes were overgrown with weeds and tall grasses which extended down to the edge of water (tr''igure 4), The influent was raw sewage that had been ground up by a communitor. This raw sewage was then discharged into the center of the prirnary cell. The effluent is piped frorn the secondary cell and is discharged into the'Willarnette River. 10

EARTHEN DYKE

U Effluent Pipe

Figure 3 . Experirnental waste water lagoon plan, Corvallis, Oregon, L963. ll

Figure 4. Eaet cell of the experirnental waEte water lagoon showing grass growing along . the periphery of the lagoon.

Figure 5. Agricultural waste water lagoon at the hog farrn, Oregon State Unlversity. lz

The agricultural waste water lagoon is located 400 yards south weet of the hog barns at Oregon State University. This lagoon is 85 feEt square (Figure 5) and the bottorn slopes down to a depth of four feet. The influent consiets of wastes frorn the hog barn and is dis' charged into the center of the lagoon. The effluent discharges into an o1d ox-bow of Oak Creek (Figure 6). As unetabilized solids are prematurely discharged into the ox-bow, tfris serves ae a secondary cell for an overloaded disposal facility. Consequently, the water in ghe rrsecondary cellt' is aleo anaerobic and ugually grades into a pro' gressively aerobie condition 50 to I00 yards north of the facility.

Figurc 6. Old ox-borr of Oak CrecL thoring thc result of effluent frorn the agricultural waste water lagoon. 13

PHYSICAL AND CHEMICAL FINDINGS

To obtain a greater understanding of ecological requirernents, and the rnicro-distribution of insects in the waste-water lagoon, chemical and physical data were collected on a routine basis from the secondary cell when facilities were rnade available (Table I ).

Influent Quality

Since the five-day biochernical oxygen dernand (BOD) is the rnost widely accepted pararneter for the arnount of decornposable organic rnaterial present in sewage, this ilreasure was used as the prinLiple loading criterion for the lagoon. Five-day BOD is defined as the quantity of dissolved oxygen needed in pprn, during stabiliza- tion of decornposable organic rnatter by aerobic biochernical action while incubated for five days in the dark at 2OoC, (1, p. ?.601. It is known frorn previous work (7, 1I) that the experimental waste water lagoon receives an average BOD loading of 60 pounds Per acre Per day. As the influent quality is highly variable, the loading also fluctuates frorn ?5 to 100 pounds of BOD Per acre per day throughout the year. The usual loading in a rnaritirne climate, for sewage sta- bilization lagoons in aerobic celIs, is frorn Z0 to 30 pounds of BOD per acre per day l3Z, p. 15). As the waste-water lagoon at Corvallis received influent frorn a vegetable canning industry in the surnmer, Table I . Dissolved oxygen deterrninations, ternperature readings, and algal sarnples taken frorn the experirnental waste water lagoon, Corvallis, Oregon.

Dissolved Oxygen in Parts per Million Ternperature oF Wet Packed Volurne of Prirnary Cell Secondary Cell Algae rnl. / I00 rnl. L9 63 Surface Bottorn Surface Bottorn Water Air Prirnary Secondary

Sept. I t 0.0 0.0 14. 0 3.0 67 76 0. 10 0,20 l3 0.0 0.0 I.3 0.0 69 77 0.05 0.10 20 0.0 0.0 16. 5 3.5 67 77 0.05 0. r2 z3 II.O 0.0 15. 0 2.5 6r 67 0. I0 0. 15 z5 9.5 0.0 18. 5 3.0 68 76 0. 10 0. I5 30 19. 0 5.0 67 75 0.15

Oct. 25 I3.0 18. 5 6.5 53 57 Nov. 26 I4.0 r6.0 3.0 5b 6Z Dec. z6 I5. I 6.2 44 50

19 64 Jan. 25 tz. z 7.8 43 50 Feb. 28 rg.4 t0. z 51 48

A 15

the loadings at tirnes were in excess of 100 pounds of BOD per acre

per day. This shock loading creates a sudden oxygen dernand on the waste water facility, and low oxygen tensions or cornplete anaerobiosis with its attendant natural conseguences result.

Dissolved Oxygen Relationship

The dissolved oxygen relationships are of importance in under-

standing the rnicro-distribution of insects in waste water habitats.

In a study of reaeration mechanics, Burgess concluded that:

Reaeration at the lagoon surface by transfer of oxygen across the liquid-air interface is of considerable irn- portance in oxidation lagoons. \{hile the principle source of dissolved oxygen is frorn photosynthetic pro- duction by a1gae, this rnechanisrn depends upon rnainte- nance of an adequate plankton population. Several fac- tors rnay severely lirnit or destroy plytoplankton growth, These include toxic rnaterials, overloading, large bloorns of rotifers or crustacea, ed:austion of nutrients, and other environrnental changes unsuited to good algae production. A rnajor source of trouble has been en- countered in the experirnental oxidation lagoon during periods of highly colored beet canning wastes, which severely reduce the light extinction coefficient and, hence, algal activity. During any period of low oxygen production by algae, reaeration frorn the surface is the principle source of oxygen (11, p. f9).

During the present study it was observed that photosynthesis of algal plankton was the rnain source of oxygen production except for seven days or so in September, when due to poor light penetration result- ing from highly colored influent wastes, the lagoon failed and becarne anaerobic (Table I ). L6

The rernaining algal suspension in the primary cell at the tirne of failure was concentrated in the top six inches of water, Below this level the water had a deep red color due to cannerywastes.

Data collected on Septernber 11 (Table 1) show that wet packed volume of algae frorn the surface of the primary cell is only half the arnount

recovered in sarnples from the secondary ceIl. The algal sarnple from the prirnary cell was pale green to yellowish in color due to lack of chlorophyll. Algae in this condition are rnature cells that are reproducing and growing very slow1y, produce less oxygen than they respire and tend to settle out and forrn sludge l?9, p. Z7Z),

This a1ga1 senescence in the prirnary cell indicates the a1ga1 cells are not reproducing and the surviving portions of the bloorn are not producing adequate arnounts of oxygen to satisfy the total dernand.

The surviving alga1 population is a liability in the function of the lagoon in that the aging and dead algal cells are exerting an oxygen dernand on the stabilization rnechanisrn. AIgaI death and senescence is probably due to increased light extinction and excessive arnounts of toxic rnetabolic by-products given off by anaerobic bacteria.

A1gal sarnples frorn the secondary cell were bright green in color and photosynthesis was active as indicated by the high arnount of dissolved oxygen. However, on Septernber 11, the secondary cell showed irnpending signs of failure, and on Septernber I3, low algal packed wet volurne and dissolved oxygen indicated anaerobic 't7

conditions throughout the entire lagoon.

At this tirne, loading of the lagoon was discontinued until

aerobic conditions could fs re-established. After a period of seven

days the secondary cell had fully recovered and loading was resurned

on Septernber 20. Aerobic conditions prevailed in the secondary celI

throughout the rernainder of this work (Figure 1Q, Page 25).

Under aerobic conditions, oxygen production in the lagoon is

affected by algal species, density of algal cells, ternperature, and

quality of wastes being stabilized. Interpretation of dissolved oxy"gen

content in the lagoon at any tirne becomes impossible without con-

sidering the diurnal periodicity of oxygen production by algal photo- synthesis (Table 2 ). For this reaoon dissolved oxygen sarnples were taken consistently at 2:00 P. M. Pacific Daylight-saving Tirne

until Novernber L963, when sarnpling was done at 2:00 P. M. Standard

Tirne.

Since dissolved oxygen decreases with depth (27, p. 39I), de-

terrninations were rnade at various depths along the south transect (Table 3 ). The dissolved oxygen content rapidly increased with distance frorn the shore until a rnaxirnurn of 17.2 ppm was obtained

at station four at a depth of 1,3 feet. The dissolved oxygen content

then gradually decreased in arnount until the rninirnurn of 10.2 pprn was reached at station ten. The surface reading at station ten sh.owed

a rnaxirnurn dissolved oxygen of 19.4 ppm. These results can be 18

Table Z Diurnal variation of dissolved oxygen content at the surface of the secondary cell. February 28, L964.

Tirne of Dissolved Oxygen Water Ternp. Air Ternp. Day (pprrr) (oF) (or)

8:00 A. M. 8.6 48 44 l0:00 A. M. LZ.5 49 45 12:00 A. M. L4.0 50 46

2:15 P. M. t9.4 51 48

4:00 P. M. L8. Z 50 48 6:00 P. M. 17. I 50 42

Table Dissolved oxygen gradient in pprn to water depth and distance frorn the shore. South transect, waste water lagoon. 2 P. M. February 28, L964.

Station Dis solved Distance Frorn Depth In No. 02 pprn. Shore In Fe e t Feet

z L4. Z z 0.5 4 L7, ? 4 1.3

5 L5. Z 6 2.0

8 LZ. L 8 2.6 IO L0. z t0 3.0 10'l' L9.4 10 0.5

'1. This represents dissolved oxygen value at the surface of Station 10. 19 explained by considering the slow diffusion rate of dissolved oxygen in water. The rrsurfacerr reading of 19.4 at. station ten shows that the dissolved oxygen is supersaturated at this depth ( Table 3 ).

This is because the rnaxinlurn oxygen production is obtained by algaL photosynthesis at this depth, and as diffusion is slow it does not readily escape to the atrnosphere.

The lower reading of 14.2 pprn near the shore at essentially the same depth as the surface reading at station ten, is rnuch lower because turbulence due to wave action enables dissolved oxygen to diffuse to the atrnosphere more rapidly. Also there is less volurne of water at this station, and consequently less a1ga1 volurne for the photosynthetic production of oxygen at this station.

Sludge Deposition

Sludge deposition rates rnay have sorne effect on the bottorn fauna. This deposition rate varies directly with an increase in or- ganic load. This load consists of biochernical oxidation dernanding substances (BOD) and can be present as a solution, a suspension, or chernically bound in bodies of living organisrns such as bacteria and a1gae.

Most of the non-living BOD is stabilized in the aerobic water zotTe well above the bottom sludge blanket. About 30 to 40 percent of this BOD load settles to the bottorn and concentrates there as ZO

sludge (25, p, 108). To obtain relative deposition rates of sludge in

the prirnary and secondary cells of the lagoon, core sarnples were

taken at each transect (Figures 7, 8, and 9). The rneasurernents

of sludge depths are given in Table 4, and this data also illustrates

that a general reduction in sludge deposition as one proceeds from

the prirnary cell through the secondary cell.

Chernical Observations at a Farrn Stabilization Pond

Chemical conditions in the agricultural waste water pond re-

rnained relatively stable throughout thie investigation. Initial dis-

solved oxygen determinations proved negative, Since conditions of

the pond could be deterrnined by visual inspection, chernical tests were discontinued. Tab1e 4 Variation in depth of core sarnples of bottorn sludge to water depth in feet. W'aste water lagoon, February 28, L964.

Station Prirnary Cell Secondary Cell 'Water Depth Dist. Frorn No. North Transect East Transect South Transect In Feet Shore in Feet

I . I5 .10 .00 0.3 I

z .zo . r6 .10 0.5 z

3 ,32 .24 .zo 0.8 3 4 .36 .36 .30 I.3 4

5 .42 .38 .30 L.4 5

6 .50 .42 .34 z.o 6

7 .50 .42 .36 2.4 7

8 .52 .42 .40 2.6 8

9 .50 .42 .42 2.8 9 IO .52 .46 .48 3.0 10

N 2Z

I E 7 6 s 4 3 :" :l

Figure 7 , Corc aamples from the north tranaect showing an increase of sludge deposition with an increase in water depth and distance of etation from the ahore in feet.

I B 7 5 5 I 3 '.2 I

Figure 8 . Core samplea frorn the eaet traneect showing an increaae of sludge depoaition with an increase in water depth and distance of station from the shore in feet. 23

-

7 6 5 4 :3 ia rl

Figure 9 Core sarnples frorn the south transect showing an increase of sludge deposition with an increa6e in water depth and distance of station from the shore in feet. Figure 10. Dissolved oxygen deterrninations of sarnples taken frorn the secondary cell. Experirnental waste-water lagoon, Corvallis, Oregon.

- o-o - Surface sarnples. - . a - Bottorn sarnples.

- o ------o - Saturation of dissolved oxygen in water at prevailing ternpe rature s. 25 I

H d b

o

\ \ ?

I

I

I

I

I

I

I oI \ \ \ \ \ \ \ t\ o: ,b \

'u:dd ue8{xo peAIos src ?6

BIOLOGICAL RESULTS

The following investigations were conducted at the experimental waste water lagoon at Corvallis. The stabilization rnechanisrn of this lagoon provided an abundant food supply for bacterial and algal rrlasses. Suspended in the water, these rnasses supported populations of grazing Entornostraca, These srnall crustaceans occurred in enorlnous nurnbers. The species cornposition changed throughout the seasons, but chiefly consisted of Daphnia and Cyclops populations.

'W'hen these crustacea settle to the bottorn of the lagoon they probably serve as food for rnany irnrnature insects belonging to tf:e farnilies

Aeschnidae, Notonectidae and the Corixidae.

Bacterial and a1ga1 rnasses that settle to the bottom and forrn sludge, provide food for large nurnbers of sewage worrns, Tubifex sp. These oligochaets live in tubes that they construct in the sludge blanket, and these too tnay serve as food for rrrany insect specie s during sorne stage of their developrnent.

The insect species found consisted of rnany diverse species and are listed in Table 5 . Due to the seasonal occurrence of sorne insect farnilies and the total elirnination of some farnily groups by adverse environrnental conditions, the ternporal distribution of in- sect farnilies in the lagoon are graphically illustrated in Figure 11. 27

Table 5 .. Insects recovered frorn the experirnental waste stabilization lagoon at Corvallis, Oregon.

Order Family Genus and Species

Odonata Aeschnidae . Aeschna rnulticolor Hagen Herniptera Saldidae Saldula cornatula Parshley Gerridae Gerris incognitus Drake and Ftrarris Notonectidae, Notonecta undulata Say Corixidae . . . Hespercorixalaevigata(UhIer) Callicorixa audeni Hungerford Callicorixa vulne rata (UhIe r) Coenocorixa sp. Corisella edulis (Charnpion) Coleoptera .Dytiscidae. Agabus strigulosus (Crotch) (Degeer) Gyrinidae . Gyrinus punctellus Ochs Hydrophilidae Tropisternus lateralis (Fabricius) Haliplidae. . Peltodytes callosus (LeConte) Diptera. .Psychodidae. Psychoda alternata Say Culicidae Culex tarsalis Coquillett Culex peus Speiser

Cu1ex pipiens Linnaeus Culiseta incidens (Thornson) Chironornidae Procladius sp. Chironornus sp. Syrphidae . . Eristalis tenax (Linnaeus) Dolichopodidae. . Dolichopus cavatus Van Duzee vagans Loew Hydrophorus gratiosus Aldrich I'igure 11. Ternporal distribution of insect farnilies occurring at the experirnental waste water lagoon showing the effect of anaerobiasis during Septernber.

Order Farnily May June July Aog Sept I oct Nov Dec Jan Feb Odonata. .Aes chnidae

Hernipte ra .SaIdidae Gerridae Notonectidae

Corixidae Coleoptera .Dytiscidae Gyrinidae Hydrophilidae Haliplidae

Dipte ra . .Psychodidae Culicidae Chironornidae Syrphidae Dolichopodidae

N m z9

Order Odonata

Many different species of Odonata were seen in flight over the

lagoon frorn June to Septernber. However, only one n.aiad exuvia of

Aecshna multicolor Hagen was collected. This exuvia was {ound

attached to the boat dock in the prirnary cell indicating that this

species had spent its naiad life in the lagoon and had clirnbed up

frorn the water to the boat dock where it ernerged as an adu1t.

Further investigation with an aquatic collecting net showed that a

fairly large population of naiad A. multicolor were present near the

errrergent grass growing in the water at the edge of the lagoon.

O:der Herniptera

Herniptera were well represented frorn July to Septernber when, due to anaerobic conditions, the populations were either re- duced or disappeared entirely.

Saldula cornatula Parshley were collected frorn those parts of the shore line that rernained darnp, yet exposed to open sunlight for the greater part of the day. These were never found rnore than six inches frorn the waterts edge. S. cornatula p""aaceous and can ".. be seen foraging about the shore line with typical quick erratic rnov€- rnents seeking srnall insect life that rnay have washed ashore.

The water strider, Gerris incognitus Drake and Harris, was 30

collected frorn the surface of the water about a foot frorn the shore line. This species was also recovered frorn the water surface pro-

tected by overhanging grass at the edge of the lagoon. Only the

rnacropterous adults of G. incognitus were recovered frorn the

lagoon.

The farnily Corixidae was the rnost nurnerous of the Herniptera recovered frorn the lagoon. Five species were found (Tab1e 5 ) and

these were recovered frorn the shallow water close to the shore.

These species were present along the entire shore line, but were

rnore abundant in those areas where ernergent vegetation was abun-

dant. None of these species were recovered frorrr water depths of

rnore than one foot.

The Notonectidae was represented by one species, Notonecta undulata Say. This species has the same rnicro-distribution, and

is found under the sarne conditions as the Corixidae.

Order Coleoptera

Representatives of five farnilies of Coleoptera were recovered frorn the lagoon. Dytiscidae were represented by two species,

Agahrs strigulosus (Crotch), and Hydroporus griseostriatus (Degeer).

The adults of these species were present in the lagoon frorn May

until Septernber. tr'rorn October untiL February 1964 only larval

forrns of these species were recovered, 3t

Adults of the farnily Gyrinidae, Gyrinus ptlnctellus ochs, were

collected in July and August. These were recovered frorn the sur-

face of the water that was Protected by the cover of overhanging

edge of the lagoon. Only one or two individuals were t grass at the collected at a tirne and no larva1 stages of this sPecies were encount- H ered.

!.rorn May until August, both adults and larvae of one species

of Hydrophilidae were collected, Tropisternus lateralis (Fabricius)

was found at the periphery of the lagoon in shallow water, OnIy lar- val forms of this species were encountered after Septernber. The farnily Haliplidae was rePresented by one speci"s, ry- dytes callosus (Le Conte). This species was found crawling alnong

the filarnentous algae growing on subrnerged grasses at the periphery

of the lagoon. P. callosus was not present after Septernber and the

larva1 forrns were not encountered at any tirne.

Orde,r DipteTa

Representatives of five farnilies of Diptera were present at various periods during this study. The larvae o{ Psychoda alternata

Say, were recovered frorn organic rnaterial that had collected at the I edge of the lagoon, particularly in the corners where the water is sornetirnee in a septic condition. Adulta of 3' alternata were re-

covered in the emergence trap frorn July until Septernber when they 3?, reached their rnaxirnurn nurnbers as the lagoon becarne anaerobic.

Larvae of four species of family Culicidae becarne very abun- dant during Septernber. These rnosquito populations consisted of

Cu1ex tarsalis Coquillett, 9. pu.rt Speiser, and C. pipiens Linnaeus. Culeseta incidens (Thornson) was encountered very infrequently and did not reach high population numbers. A11 of the mosquito speci.es were usually found in protected areas at the periphery of the lagoon and in the grasses growing at the surface of the water along the wooden partition between the two ceIls.

In order to rnake a survey of the bottom fauna, a transect of the primary cell of the lagoon was rnade by sarrpling with a six- inch square Eckrnan dredge in August. No insects were recovered frorn tl:e central area of the lagoon. Qualitative sarnpling by drag- ging an aquatic collecting net across the bottorn from a drifting boat, showed that no insects occurred beyond eight feet from the shore at depths varying from three to four feet at any tirne during this investi- gation.

Further sarnpling with the Eckrnan dredge revealed that a popu- lation of larval Chironornidae was present about seven feet frorn the shoreline. The depth distribution given in Table 5 shows that this population gradually increased in nurnbers to a rnaxirnurn of eight larvae per 36 square inches of bottorrr area sarnpled at a depth of

L.Z feet, 33

Table 6 . Nurnbers of larval Chironornidae recovered by 5 inch square dredge sarnples. North transect, prirnary ceIl, waste water lagoon. August 2, L963.

Station Procladius Chironornus Dist. Frorn Depth No. sPecle s Shore in Feet in Feet

I 0 0 t 0.3 z 3 I z 0.6 3 6 0 3 0.8 4 7 I 4 L.Z 5 z 5 5 L,4 6 0 7 6 2"0 7 0 z I 2,4 8 0 I 8 2,6 9 0 0 9 Z,B IO 0 0 10 3.0

The nurnbers of larvae gradually decreased toward the shore line until none was recovered frorn station one at depth of 0, 3 f.eet.

A sirnilar transect was rnade in the secondary cell (Table 7).

This shows that in the secondary cell there is a sharp increase in Procladius sp. larvae and that rnaxirnurn nurnbers were recovered frorn station five at L.4 f.eet depth. A third transect was made near the effluent at the south side of the secondary cell, Table 8 In this transect Procladius sp. were at their greatest nurnbers at station six at a depth of two feet. Only one thironornus sp. was recovered frorn station seven at ?.4 feet. This seerns to be the optirnurn depth for Chironomus sp. in the secondary cell. Spot checks in areas ad- jacent to the transects being investigated indicate the above.figures 34

Table 7 . Nurnbers of larval Chironornidae recovered by 6 inch sguare dredge sarnples. East transect, secondary ce11, waste water lagoon, Corvallis, August 5, L963,

Station Procladius Chironornus Dist. Frorn Depth No. Specie s Specie s Shore in Feet In Feet

I 0 0 I 0.3 2 3 0 z 0.5 3 6 0 3 0.8 4 8 0 4 L,Z 5 IO I 5 t,4 6 4 0 6 2.0 7 I z 7 2,4 8 0 t 8 2.6 9 0 0 9 2,8 IO 0 0 10 3.0

Table 8 Nurnbers of larval Chironornidae recovered by 5 inch square dredge sarnples. South transect, secondary cell, waste water lagoon, Corvallis. August 9, 1963,

Station Procladius Chironornus Dist. Frorn Depth No. Specie s Specie s Shore in Feet In Feet

I 0 0 I 0.3 z z 0 2 0.6 3 3 0 3 0.8 4 z 0 4 t.2 5 5 0 5 L,4 6 I5 0 6 2,0 7 4 t 7 2,4 8 0 0 8 2,6 9 0 0 9 2,8 t0 0 0 IO 3.0 35 do represent the true rnicro-distributions of the chironornid popula- tions.

In order to obtain more inforrnation on the bottorn insect fauna in winter, a second series of transects were rnade in February L964,

In the primary cel1, Table g , there is a drastic reduction in the Procladius population with only two specirnens being recovered at station two at a depth of 0. 6 feet. The Chironornus population show- ed an overall decrease in population with a total of nine specirnens recovered frorn the transect. Flowever, the Chironornus species were in greater numbers nearer the shore with three specimens be- ing recovered at station two. In the secondary cell, Table IO the

Procladius population showed an increase with a rnaximurn nurnber occurring at station six. The Chironomus population also showed an increase and the greatest nurnber was found eight feet frorn the shore at a depth of. 2.6 f.eet.

In the third transect of this winter series, Table I L the re- sults are similar to those of Table I0. In this respect these trvo transects are replicates of each other. Spot checks taken at the other side of the boat and frorn areas other than the transect line itself showed that each transect made did reflect the true population densities and that the populations were evenly distributed around the periphery in each ceII. of the Diptera found at the experirnental waste water lagoon, 36

Table 9 Nurnbers of larva1 Chironornidae recovered by 6 inch square dredge sarnples, North transect, prirnary cell, waste water lagoon, Corvallis, FebruatY 6, L964.

Station Procladius Chironornus Dist. Frorn Depth No. Species -@s Shore in Feet In Feet

I 0 0 I 0.3 z Z 3 Z 0.6 3 0 I 3 0.8 4 0 z 4 L.2 5 0 z 5 L,4 6 0 I 6 Z,O 7 0 0 I 2,4 8 0 0 8 2,6 9 0 0 9 2.8 IO 0 0 t0 3.0

Tab1e I0. Nurnbers of larval Chironornidae recovered by 6 inch square dredge samples. East transect, secondary ceII, waste lagoon, Corvallis, February 7, L964,

Station Procladius Chironornus Dist. Frorn Depth No. -@s- Specie s Shore in Feet In Feet

t 0 0 I 0.3 Z 5 0 Z 0.6 3 4 0 3 0.8 4 3 I 4 L,Z 5 5 I 5 L,4 6 7 0 6 2.0 7 4 3 I 2.4 8 0 5 8 2,6 9 I 3 9 2.8 t0 0 0 t0 3.0 37

Table t 1. Nurnbers of larval chironornidae recovered by 5 inch square dredge sarnples. South transect, secondary ce11, waste water lagoon, Corvallis, February 10, L964'

Station Procladius Chironornus Dist. From Depth No. -Epe"-- Specie s Shore in Feet In Feet

I 0 0 I 0.3 Z 4 0 2 0.6 3 3 I 3 0. B 4 6 3 4 L,Z 5 4 I 5 L,4 6 8 4 6 Z,O 7 9 5 7 2.4 8 4 4 B 2.6 9 0 I 9 2,8 10 0 0 10 3.0

the Syrphidae were the least abundant. Pupae and adults were not encountered at this location. The larvae of Eristalis tenax (Linnaeus), known as rat-tailed rnaggots, could be found only in isolated pockets forrned by sparse floating organic rnaterial in the corners of the lagoon. Soil adjacent to the water was searched for pupae of the

Syrphidae but none was recovered.

Mernbers of the Dolichopodidae were abundant frorn June through August. In Septernber they suddenly disappeared at the sarne tirne as the farnily Gerridae. The adults of Dolichopodidae were frequently taken frorn the surface of the rnud at the shore line. Their larvae were not encountered, but rnany rnud encased pupae were collected one inch below the surface of the soil near the waterrs edge. These pupae were taken to the laboratory and the adults 38 errerged after two weeks. The adults could also be seen on the sur- face of the water about a foot {rorn the shore, but greater nurnbers preferred the shore in open sunlight.

Laboratory Obse rvations

To obtain a better understanding of the differences in rnicro- distribution and population density between the two species of Chi- ronornidae, larvae were collected in the field and reared in labora- tory to observe dif{erences in their biology.

Larval Chironornus sp.kept in the laboratory at room tempera- ture (ZZo to Z3oCl were very active. The larvae are protected by tubes rnade of particles of coarse detritus which are sealed together with salivary secretions. \Mhen larvae are placed in one gallon jars containing water and sludge frorn their natural habitat, the water soon becornes depleted of oxygen. The Chironornus larvae respond to this low oxygen tension by leaving their tubes to swirn through the water with a lashing rnovelnent. Occasionally they rise to the sur- face as if to renew their oxygen supply.

In the absence of aeration the tubificid worrns frorn the sub- strate will also rise to the surface and forrn a red mat. After a few days the jar becornes rnore anaerobic and the organisrns therein becorne rnotionless. Chironornus larvae treated in this rnanner all die within three to seven daYs. 39

Larval Chironornus sP. placed in jars at roorn ternperature as above, but with pressure aeration, ernerged after 30 to 40 days, de- pending upon the stage of rnaturity. The environrnent inside the rearing jars was observed to develop into one of two characteristic types. One type was characterized by a heavy susPension of algae and no grazing organisrns. The other type of environrnent developed crystal clear water with a population of grazing entomostraca. In either situation, and with the addition of srnall arnounts of organic rnaterial in the forrn of ground up dog food, larval Chironornidae found conditions suitable for growth and developrnent.

Larval activity was rnore clearly seen by placing thern in petri dishes of clear water with a small arnount of stabilized detritus frorn an aquariurn. This environrnent had an adequate dissolved oxygen level and rernained stable throughout the periods of observa- tion. Six petri dishes were prepared and one larva of Chironomus constructed fresh a"t." sp. was placed in each. The larvae "-r- night and were observed irrigating their tubes for one or two rninutes at approxirnately three rninute intervals. For two or three days the larvae occupied these tubes and obtained food by extending their bodies frorn the tube to feed on detritus. After feeding in this position for about ten rninutes, a larva will withdraw into its tube and carry out respiratory undulations thus irrigating the tube for one or two rninutes. The larva then ceases undulating and reverses its position 40 in the tube to face the opposite direction and extends its body from the other end of the tube and continues foraging for food. After each reversal in the tube the larvae extend their feeding activity to great- er distances frorn the tube. This behavior continues until an area of

20 rnrn. in radius is cleared frorn each end of the tube. As the lar- vae were kept for 30 to 40 days in these petri dishes, the foraging excursions for {ood becarne rnore frequent and after a period of seven days the larvae would leave their tubes for greater lengths of time. At tirnes a larva would not return to its old tube but would construct a tube at another location in the dish.

Of these six Chironornus larvae observed one died after seven days, a second larva died after l5 days, and the four rernaining pupated and transforrned to adults after 30, 31, 35, and 40 days.

Larval Procladius sp. , when kept in the laboratory at room ternperature, do not rnake tubes but are continually in rnotion at the surface of the substrate. When this species is subjected to an anaerobic environrnent in a gallon jar it does not swirn to the uPper layers of oxygenated strata, but will crawl rapidly along the sub- strate then rest. Treated in this trranner, Procladius larvae will becorne less active as anaerobiosis proceeds. After eight to 24 hours of anaerobiosis this species dies. The larva of Procladius sp. have a relatively rapid growth rate, Larvae of this species reared in the laboratory at roorn ternperature, ernerged frorn five 4L to ten days later. This species is less tolerant to anaerobiosis than is Chironolrrus sp. , and could not be reared in the laboratory in one gallon jars containing their natural substrate at room ternperature, without pressure aeration.

Observations at a Farrn Stabilization Pond

To gain rrrore information about insects associated with waste water, observations were also rnade at an agricultural stabilization pond. This facility was designed to dispose of wastes frorn hog barns at Oregon State University. During a prelirninary survey in July, a few individuals of SaIduIa comatula were seen running about the soit at the shore line. Only a few adults were found on later oc- casions and these probably migrated from Oak Creek which is situat- ed 100 yards west of the pond.

Many adult of the family syrphidae were collected near the water in JuIy. These were the adults of the cornmon rat-tailed rnaggot, a frequent inhabitant of stagnant pools of high organic con- tent. Very large nurnbers of Eristalis tenax rnade up this population.

The adult gravid fernale of this species could be seen hovering a few inches above the water level and frequently alighting on the soil and debris to oviposit. The eggs were not exposed, but well hidden a half inch or so in cracks of the soil. These were laid in clusters of

ZO to 30 at each oviposition site. The ova were oblong in shape, 42 white in color, and are sirnilar to those of the cornrnon BIow-, Calliphora vornitoria (Linnaeus). The larvae of E. tenax could be

recovered frorn the water in huge tangled rnasses. These were found at the strore line and at a distance extending about six inches from the

shore. At this point the water was six inches deep and the bottorn

sloped down to four feet in the center of the pond.

No larvae were found at depths greater than six inches. This is because the larvae cannot extend their breathing tubes beyond this distance. However, the larvae can float at the surface, and they are often observed in this position with their breathing tubes extended into a tangled rrrass. Individual larvae can be seen crawling upon the underside of the surface filrn, and in this way can extend their activities out considerable distances frorn the shore line over the deepest water.

The larvae leave the water and pupate in the soil and debris

at the shore line. These are yellow to brown in color, and most of thern are found one inch below the surface of the soil. At tirnes the

pupae may be so abundant that vast nurnbers of thern rnay be seen

lying at the soil surface. Field dissections of these exposed PuPae

showed they were all a1ive. These probably represented a srnall

fraction of the total population that exhibited variation in behavior,

as would be expected in biological rnaterial, and pupated at the soil

surface instead of burrowing below. 43

The only other species found actually breeding in the stabiliza- tion pond was the so-called drain fly, Psychoda alternata. In Septern- ber the adults of this species could be found in protected areas in the grass growing at the side of the pond. The larvae of this species were found in floating mats of organic rnaterial at the surface of the pond. As the larvae of P. alternata are air breathers, none was re- covered frorn the bottorn of the pond.

After October there was very little insect activity at the farrn stabilization pond and no adults or larvae of any species were found here in the winter. 44

DISCUSSION

The environrnent of the insect fauna in this study is artificially created by rnan as a facility for the biological treatrnent of waste water. Stagnant water of high organic content occurs in nature, and conditions for optirnurn developrnent of insects adapted to these waters occurred before the advent of civilization.

Water of high organic content can be found in rock depressions of the spray zone along the coast. In such situations mernbers of the farnily Corixidae can develop to rnaturity, providing water is re- plenished occasionally by spray frorn the sea at high tides. When such rnicro-habitats becorne enriched by the introduction of sea weeds and becorne septic, rat-tailed maggots are usually found breeding in thern. These flies also breed in tree holes containing septic water,

Sorne species of rnosquitoes are well known for their wide choice of aquatic habitats containing varying degrees of organic content.

Mernbers of the farnily Chironornidae are found norrnally oc- curring in nature in great nurnbers under a wide variety of conditions.

Chironornus species in particular are well adapted to the profundal regions of lakes containing sedirnents rich in organic rnaterial. Sirnilar aquatic situations of high organic content could be cited Ior all the insect species occurring in waste water lagoons. The species cornposition and population structure may be unique in rnodern waste 45 water lagoons, but these insect species undoubtedly occurred in this region before civilized rnankind.

Due to rapidly changing environrnental conditions in the experi- rnental waste water lagoon, any resident insect population rnust be either tolerant to these fluctuations, have resistant stages, or be able to rnigrate to other bodies of water. Perrnanent populations are those species that have an active aquatic stage present in the lagoon at all tirnes. Seasonal populations are those species having aquatic stages present during certain tirnes of the year, Transienr populations are those species having an active aquatic stage that is able to rnigrate to or frorn other bodies of water.

The only perrrranent insect populations in lagoon are the irn- rnature stages of the Chironornidae. Insect populations such as the rnosquitoes are seasonal when it is considered that they spend only a short larval period in the lagoon each year.

Even when the most favorable conditions in the lagoon were present, all the insect groups confined their activities to the peri- pheral portions of the lagoon. This is also true for the Chirono- rnidae, that are to sorne extent adapted to oxygen lack, and are con- fined in their rnicro-distribution to the shallower bottorn substrate near the periphery of the lagoon.

Frorn May to Septernber, environrnental conditions for aquatic insects at the waste water lagoon were relatively constant. In 46

Septernber, failure occurred in the prirnary cell and was followed by anaerobic conditions in the secondary cell also. The principal cause of this failure was due to large loadings of highly colored beet can- nery wastes which reduced photosynthesis by light extinction in the lagoon. The reduction in nurnber of insect species in the lagoon is due to fluctuation in environrnental conditions,

The dragonfly E. rnulticolor quickly repopulated the lagoon in late Septernber and this species probably survived the unfavorable anaerobic period as eggs. Many naiads of this species were reared in the laboratory frorn eggs collected with mud in August,

A11 the Herniptera suddenly disappeared in Septernber. Mern- bers of this order probably took flight to neighboring bodies of water.

W'hen the lagoon environment for these insects irnproved again later in Septernber, the Corixidae and the Notonectidae returned. The

Corixidae were reproducing and developing in the lagoon and rnany irnrnature stages of these insects were recovered frorn the periphery of each cell.

The water strider G. incognitus did not repopulate the lagoon after the period of anaerobiosis in Septernber. It was abundant in

July and August, but it is not known if it was actually reproducing at the lagoon or if it was part transient. These were all rnacropterous adults and no apterous forrns were found. Apterous and rnacrop- terous rnernbers of the farnily Gerridae occur sirnultaneously in 47 identical environrnents, though varying in relative frequencies in different species and possibly with certain seasonal or other external factors. It is thought that the Presence of wings might offer sorne handicap to active life on the surface f:-Lrn (24, p. 137), ancl that individuals possessing the rnacropterous condition would be selected against in nature and produce fewer progeny. Once this condition was rnade available in the gene pool by rnutation, natural selection would account for the persistence apterous forlrls. However, should the environrnent change so that rnigration by flight was necessary in order to survive, rnacropterous forrns would then be selected for in nature. As the population of G. incognitus at the waste water lagoon maintained the rnacropterous condition, they were probably adapted to a changing environrnent such as ponds that dry up in late sulnlne r.

Larvae of the Dytiscidae and the Hydrophilidae were recovered after Septernber, indicating that these two farnilies had re-established themselves. Other farnilies of the Coleoptera listed are probably transitory, as only adults were recovered frorn the lagoon.

A11 the larval Diptera recovered are adapted in sorne degree to oxygen lack. Frorn June to August, Dolichipopidae were present and were reproducing in the lagoon, as the adults were reared frorn pupae collected in the peripheral soil. However, this farnily did not becorne re-established after the anaerobic period in Septernber. 48 The reason that Syrphidae were not encountered in very great nurnbers at the experirnental waste water lagoon is that perrnanent septic conditions for the developrnent of larval E. tenax did not exist.

Larval E. tenax are adapted to aquatic situations having a high or:gan- ic content that are usually septic. The larvae are equipped to breathe atrnospheric oxygen by extending their breathing tubes to the surface of their aquatic rnediurn. Larvae living under these conditions have an arnple food supply and are virtually free frorn predators. How- ever, should the rnicrohabitat change, as it often did in the waste water lagoon, predators could lrrove in and destroy the larvae of E. teqqr. This probably occurs at the lagoon on occasions when the pre- vailing wind changes and disperses clurnps of organic rnatter contain- ing E. tenax. The larvae would then be rernoved frorn a protected anaerobic rnicrohabitat to an aerobic environrnent containing insect predators. Thus, possibly as a result of high rnortality in the larval stages due to predation, no pupae were found in the soil adjacent to the water.

The Culicidae found optirnurn environrnental condition in the lagoon during the periods of low oxygen content. On Septernber t, rnosquito larvae in the prirnary cell were treated with a Malathion in oil solution. Mosquito larvae in the secondary ce1l were treated in the sarne rnanner seven days later. In this way fairly acceptable con- trol of rnosquito larvae was achieved without noticeably harrning the 49

larval Chironornidae which were being studied.

Larvae of the Chironornidae occupy the sludge blanket at the bottorn of the lagoon. They are restricted in distribution to the peri- pheral slopes within eight feet of the shore line (Tables 6 to 1i ).

The rnain factor preventing these larvae frorn occupying deep water is extended periods of nocturnal anaerobiasis. The accurnulation of sludge is a continuous process and occurs when soluble, colloidal, and suspended rnaterials both living and non-living, are deposited on the bottorn. Sludge accurnulations exert a sustained oxygen de- rnand upon the water layers above the bottorn. Consequently the rnicrohabitats of the Chironornidae populations are devoid of oxygen rnost of the time. 'This is particularly true at night when oxygen that has been produced by a1gal photosynthesis during the daylight hours is rapidly used up by biochernical reactions. A portion of this di- urnal fluctuation in dissolved oxygen at the surface of the lagoon is shown in Table 2 Figure l0 shows the dissolved oxygen content at the surface and at the bottorn of the secondary cell. As the solu- bility of dissolved oxygen varies inversely to a rise in ternperature, the solubility of oxygen at each recorded ternperature is also given.

The dissolved oxygen curves throughout this six rnonth period are based on sarnples taken at Zz00 P.M. when oxygen values are at their rnaxirnurn at the surface and at the bottorn of the lagoon. As the "bottornrr dissolved oxygen sarnples were taken six inches above 50 the sludge blanket, the actual dissolved oxygen values in the rnicro- habitat of the Chironornidae are unknown. Previous work (10, p. 4Zl has shown that rnicrostratification of dissolved oxygen exists at the rnud water interface in 1akes. In the larval rnicrohabitat iri the waste water lagoon, rnicrostratification and oxygen depletion at the sludge water interface are even rrrore pronounced. The Chironornus sp. observed in an anaerobic environrnent in the laboratory were seen to leave their tubes and swirn to the surface to obtain oxygen.

This behavior probably occurs in their natural rnicrohabitat under periods of anaerobiosis. That is, larval Chironornus sp. rnay leave their tubes at night to rnove about in the upper layers of water that contain rnore dissolved oxygen. Chironornus sp. are better adapted to periods of anaerobiasis than are the Procladius sp. This is due to the fact that Chironornus sp. have Erythrocruorin dissolved in their blood. This blood pigrnent acts in both the transportation and storage of oxygen. Erythrocruorin greatly increases the rate of recovery frorn periods of oxygen lack and enables the larvae to continue irrigation and feeding rnovernents (31, p. 751, Larvae of

Procladius sp. are found in the shallower portions of the lagoon.

This is because they are less adapted to periods of anaerobiosis than are the Chironomus sp. This species has the sarne lashing rnovernent as the Chironornus species, when disturbed, but they are unable to swirn in the upper strata of oxygenatedwater during periods 51 of oxygen lack.

In the secondary ce11 Procladius sp. are found in their greatest nurnbers at depths of one to two feet, where dissolved oxygen is rnore readily available. This species, being less adapted to oxygen lack, is even rnore restricted to periphery in the prirnary cell due to ex- tended periods of anaerobiasis.

However, due to the relatively rapid growth and developrnent rate of Procladius sp., these insects can quickly expand their rnicro- distribution when environrnental conditions irnprove. This explains why Procladius sp. is found in greater nurnbers in the lagoon.

Both species of Chironornidae are adapted to the quiet water of the bottorn region and are not found in the shallow areas near the shore. This is because wave action at the shore causes frequent rnovernent of the particles of the substrate and prevents the accurnu- lation of nutritive organic debris. Wave action would also abrade these insects and cause them to rnove to quiet water.

Wave action was also irnportant in controlling the rnosquito populations of the lagoon. During moderate winds, rnosquito larvae were displaced f rorn their protective habitat in ernergent grasses and were driven by wave action to exposed areas along the shore.

The larvae were then subject to abrasive action and were washed up on the shore.

To prornote wave action and its resulting physical control of 5Z

rnosquito populations, waste water lagoons should be designed with

large surface areas and low dykes. Unfortunately consistent control

by wave action cannot be relied upon, and chernical control rneasures

had to be taken during this work. However, wind action worrld

greatly reduce the nurnber oI chernical applications necessary for

the control of larval rnosquitoes.

The water in the farrn stabilization pond was black in co1or.

Undigested feed rnaterial frorn the barns floated to the surface to forrn a six inch thick rnat. This rnat undoubtedly interferes with

the surface reaeration rnechanisrn. The anaerobic condition of the

water and the extinction of tight by the rnat of floating rnaterial pre-

cludes photosynthesis by algae. As the pond is cornpletely anaerobic

at all tirnes, the insect fauna breeding there is restricted to E.

tenax and P. alternata only.

In June 1953 the effluent flowing into the old ox-bow contained

no floating solids and showed good recovery to aerobic conditions

five to ten yards frorn the discharge pipe. In this zor:e of recovery

algal growth was abundant and rnosquito breeding was at a rninirnurn,

The aerobic portion of the ox-bow supported a varied insect fauna

cornrnon to that found in srnall fresh water ponds. However, in or-

der to facilitate waste water disposal frorn the hog barns obstructions were rernoved frorn the effluent pipe to allow floating solids to be

prernaturely discharged into the ox-bow. 53

This had the effect of increasing the load in the ox-bow which now served as a secondary cell of the oxidation pond. Conseguently the water in the ox-bow becarne anaerobic and the norrnal insect fauna died or rnoved I00 yards north beyond the zone of recovery.

The change to anaerobic conditions, and the absence of a norrnal cornplirnent of insect predators frorn the septic portion of the ox-t'ow, irnproved the habitat for rnosquito breeding, In JuJ.y 1963 the ox-bow was chernically treated periodically for rnosquito control. The oxi- dation pond was operated in this manner continuously, and in Febru- ary L964 a winter insect fauna was present beyond the zone of re- covery 100 yards north of the pond, and no insect activity was noted in the septic zone of the oxidation pond. 54

SUMMARY

Insect populations of an experirnental waste water lagoon con- sisted of those species adapted to water of high organic content, and low arnounts of dissolved oxygen.

Insect populations were subject to rapid environrnental changes in the lagoon due to shock BOD loadings. In Septernber the lagoon failed and becarne anaerobic. Loading was suspended for a week to re -e stablish ae robic conditions.

Many of the species recovered were transitory residents, AL1, the Odonata and Herniptera disappeared in Septernber. In October the Odonata were again reproducing in the lagoon. The Notonectidae and the Corixidae were the only farnilies of the order Herniptera that were found in the lagoon after Septernber, but only the Corixidae were reproducing.

The populations of Coleoptera were also transient, and were present in the lagoon after Septernber. However, only the farnilies

Dytiscidae and Hydrophilidae were found breeding in the lagoon.

The farnily Dolichipodidae were also transient and was present frorn June to August, The Syrphidae at the experirnental waste water lagoon were found in isolated instances only.

Seasonal residents were represented by the farnily Culicidae.

These rnosquitoes breed in the lagoon frorn Septernber to October 55 and were controlled with a larvicide. Psychodidae were also season- aI and were found in great nurnbers in Septernber.

The most irnportant feature of the lagoon was the large populations of the farnily Chironornidae. These perrnanent residents were confined in their micro-distribution to the shallower regions at the periphery of lagoon. The rnain factor controlling the rnicro-distribution of these species is the availability of dissolved oxygen. Other factors affecting the rnicro-distribution and popula* tion structure of the insect fauna in the lagoon were bottorn sedirnents, wave action, light penetration, and the design of the lagoon.

The rnost obvious biological rnechanisrn affecting these insect species is the production of dissolved oxygen by algal photosynthesis,

Vegetation growing at the periphery of the lagoon provide food and harborage for lnany species.

The absence of an insect predator cornplex, and the heavy

BOD loading during Septernber, created a favorable environrnent for rnosquito larvae. If control rneasures had not taken effect, rnosquito breeding would have becorne a dorninant feature of the lagoon.

The dorninant anthropod feature of the farrn stabilization pond was the seasonal production of the farnilies Syrphidae and Psychodi- dae. These insects were rnost abundant in August and Septernber.

No insect activity was noted in the winter. 55

BIBLIOGRAPHY

1. Arnerican Public Health Association. Standard rnethods for tiie exarnination of water, sewage, and industrial wastes. 1Oth ed. New York Arnerican Public l{ealth Associa- tion, Inc. , L955. 5ZZ p,

Z. Barber, H. G. Aquatic Herniptera. Journal of the New York Entornological Society 2L:29-32. 1913.

3. Bartsch, Alfred F. Biological aspects of strearn pollution. Sewage Works Journal ZO:Z9Z-302. 1948.

4. Bartsch, Alfred F. Biological and chernical aspects of orgarric waste lagoons. In: Land disposal of liquid wastes. University of Wisconsin. Engineering Institute on Industrial Wastes. Madison, L956, p. 62-84,

5. Bartsch, Alfred F. and M. O. Al1urn. Biological factors in treatrnent of raw sewage in artificial ponds, Lirn- nology and Oceanography Z:77 -84. L957.

6. Bartsch, Alfred F. and W. M. Ingrarn. Strearn life and the pollution environrnent. Public Works 90(7):I04-1I0. L959.

7. Bartsch, Alfred F. A1gae as a source of oxygen in waste treat- rnent. Journal Water Pollution Control Federation 332239-249. L96L.

8. Beadle, Leslie D. and Fred C. Harrnston. Mosquitoes in sew- age stabilization ponds in the Dakotas. Mosquito News L8:293-296. 1958.

9. Bol1en, W. B. The nature of organic pollutants in relation to strearn BOD. Water and Sewage lVorks 98:277-ZBL, 195 1.

10. Brundin, Lars. The relation of oxygen rnicrostratification at the rnud surface to the ecology of the profundal bottorn fauna. Institute of Freshwater Research, Drottning- holrn, Sweden, Report 32:32-42. 1950. 57

I I. Burgess, Frederick J, et al. W'aste water tragoon criteria for rnaritirne clirnates. Progress Report no. Z, Corval- lis, Oregon State University, Engineering Experi.rnent Station, Dept. of Civil Engineering, L962. I00 p. lZ. Burlington, Roy F. Quantitative biological assessrnent of pol- lution. Journal Water Pollution Control Federation 34:170- I83. 1962.

13. Freeborn, S. B. and R, M. Bohart. The rnosquitoes of Califor- nia. Bulletin of the California Insect Survey l:lz)25- 78. 1951.

L4. Griffith, Melvin E. The environment, life history and structure of the water boatrnan, Ramphocorixa acurninata (IJtrler). University Kansas Science Bulletin 30:Z4L-365, L945,

15. Grossbeck, John. The relation of rnosquitoes to their envi.ron- rnent. Journal of the New York Entornological Society Ztz55-62. I9I3.

L6. Herrns, W'illiarn B. and Maurice T. Jarnes. Medical entornolo- gy. New York, Macrnillan Company 1961 , 6L6 p,

L7, Hicksrnan, Jennings R. Contribution to the biology of the Halipli- dae (Coleoptera). Annals of the Entornological Society of Arnerica Z4:LZ9-142. 193I.

I8. Hungerford, H. B. The biology and ecology of aquatic and serni- aquatic Hemiptera. Kansas University Science Bulletin I1:I-341. L9ZO.

L9. Lindernan, Rayrnond L. Experirnental sirnulation of winter anaerobiosis. In: A Syrnposiurn on Hydrobiology. Madison, University of Wisconsin Press, L94L. 392- 392 P. 20. Loomis, E. C. (ed. ) A field guide to cornrnon rrosquitoes of California. Entornology Cornrnittee of the California Mosquito Control Association. 1959. 26 p.

ZL. Matheson, Robert. The Haliplidae of North Arnerica, North of Mexico. Journal of the New York Entornological Society ZO;L56-L93, L9LZ. 58

ZZ. Miall, L. C. The natural history of aquatic insects. New York, Macmillan and Cornpany, I895. 395 p.

23. Ordrnan, David. Bronchial asthrna caused by the trickling se\^'- age filter fly (Psychoda):inhalant insect allergy. Nature L57:44L, L946,

24. Parshley, H. M, A note on the rnigration of certain water- striders. Bulletin of Brooklyn Entornological Society L7:L36-L37 . L922"

25. Phelps, Ear1e B. Strearn sanitation New York, John Wiley and Sons, Inc, 1944, 276 p,

26. Richrnond, Avery E. Studies on the biology of the aquatic Hy- drophilidae. Bulletin of the American Museurn of Natural History 4Z:L-94. L920,

27, Towne, W. W., Bartsch, A. F. and Davis,W. H. Raw sewage stabilization ponds in the Dakotas. Sewage and In- dustrial Waste s 377 -396, L957 . 28, Usinger, Robett L. (Ed.). Aquatic insects of California. Berkeley University of California Press 1956. 508 p.

29. Usinger, Robert L. and Kellaq W. R. The role of insects in sewage disposal beds. Hilgardia. 23:263-32L. 1955,

30. Walshe, Barbara M. On the function of haemoglobin in Chi- ronornus after oxygen lack. Journal of Experirnental A;i;gv z 4:329- 351 . 1947 . 3I. Walshe, Barbara M. The function of haernoglobin in Chirono- rnus plurnosus under natural conditions. Journal of E"r"Gffieiology z7 :73-95, 1950.

32, Wilson, John N., Jarnes H. McDerrnott and Alfred Livingston, HL Perforrnance of a sewage stabilization pond in a rnaritirne clirnate, U, S. Departrnent of Health, Education and Welfare; Washington Pollution Control Comrnission; Oregon State Sanitary Authority. L960. 41 p. (Mirneographed).