This dissertation has been microfilmed exactly as received Mie 60-6395

MURVOSH, Chad Michael. AN ECOLOGICAL STUDY OF THE RIFFLE BEETLE PSEPHENUS HERRICKI (DeKAY) (COLEOPTERA: PSEPHENIDAE). The Ohio State University, Ph.D., 1960 Zoology

University Microfilms, Inc., Ann Arbor, Michigan AN ECOLOGICAL STUDY OF THE RIFFLE BEETLE PSEPHEMJS

HERRICKI (DeKAY) (COLEOPTERA: PSEPHENIDAE)

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By

CHAD MICHAEL MJEVOSH, B. S ., M. Sc.

******

The Ohio State University 1960

Approved by

' A dviser Department of Zoology and Entomology ACKNOWLEDGMENTS

I wish to egress ray sincere appreciation to Dr. Ralph

Ho Davidson of The Ohio State University, for his advice and supervision of this investigation.

I also wish to thank Dr. Milton W. Sanderson, Dr. Richard

D. Alexander, Dr. Frank N. Young, Professor Josef N. Knull,

Dr. Hugh B. Leech, Dr. H. J. Relnhard, Dr. Glenn B. Wiggins,

Dr. Henry F. Howden, Dr. 0. L. Cartwright, Dr. Paul Spangler,

Dr. J. F. Gates Clarke, Paul Freytag, and Edwin Hazard for their aid in helping me to understand the geographic dis­ tribution of the genus Psephenus.

I am indebted to Dr. John W. Crites who examined adult and larval specimens of P. herricki for parasites.

Sincere appreciation is also extended to Dr. Frank W. Fisk,

Dr. Alvah Peterson, Dr. Willard C. Myser, Dr. Dwight M. DeLong,

Dr. Charles A. Dambach, Dr. David H. Stansberry, Dr. Clarence E.

Taft, and Dr. T. H. Langlois, who helped in more ways than it is possible to express.

i i TABLE OF CONTENTS

Page

In tro d u c tio n ...... 1

Methods . 3

Sampling Larval Populations ...... 4

Chemical Analysis of W ater ...... 7

Physical Factors ...... 8

The Study A re a ...... 12

Geographic Distribution ...... 16

Ecological Life H isto ry ...... 19

L a r v a e ...... 19

Description and Development ...... 19

F o o d ...... 23

B e h a v i o r ...... 24

Ecological Distribution ...... 32

S u r v i v a l ...... 43

Pupae ...... 52

Description ...... 52

Ecological Distribution ...... 52

S u r v i v a l ...... 54

A d u l t s ...... 56

Ecological Distribution ...... 56

i i i Page

E g g s ...... 65

Description and Development ...... 65

Ecological Distribution ...... 66

D i s c u s s i o n ...... 72

Summary ...... 81

Literature Cited ...... 85

iv TABLES

Page

1. Climatological data for Columbus, Ohio, 1959 ...... 13

2. Relationship between the number of larvae on a rock and the relative position of the r o c k ...... 30

3. Chemical conditions of habitats at Hayden Gorge . . . 36

v FIGURES

Page

1. Field data record card ...... 11

2. The North American distribution of the genus Psephenus . 18

3. The larva of Pi herricki ...... 21

4. Total length measurements of water penny larvae .... 22

5. Graph of the relative numbers of P. herricki larvae in three habitats at Hayden Gorge ...... 34

6. Map of the Hayden Gorge habitats ...... 35

7. Habitats at Hayden Gorge before flood ...... 46

8. Habitats at Hayden Gorge during flood ...... 47

9. Habitats at Hayden Gorge after flood ...... 48

10. An adult P. herricki ...... 57

v i INTRODUCTION

Any ecological study is of necessity very broad. The in­ vestigator, in approaching a problem, cannot set sharp lim its to the areas to be investigated. Many subjects will require study if the worker ever hopes to weave together the solution to a particular problem. This applies to any study but is especially true if the study is ecological in nature, since ecology is more directly con­

cerned with the interaction of variables.

This study represents an attempt to understand and explain the macrohabitat and microhabitat distribution of a species of aquatic

insect. The answers to two questions were sought: (l) What is the habitat distribution of the life stages of the water penny Psephenus herricki? (2) What factors cause such a distribution? The question may be r e s ta te d : Where does Psephenus h e r r ic k i li v e and why?

Preliminary field work showed that the larvae of this species are not restricted to any definite type of aquatic habitat. They

could be found in lakes and in riffles, runs, and pool areas of various types of streams. Qualitative sampling indicated that the

greatest numbers were found in stream riffle areas. Sampling was

then continued throughout the study on a quantitative basis to

determine whether such was actually the case and what factor or

factors were responsible for such a distribution. Quantitative data were supplemented by various laboratory experiments and by qualita­

tive observations both in the laboratory and in the field. Life

history data were collected to supplement existing information.

1 There exists very little information concerning the water beetles of the family Psephenidae. Much of this is taxonomic in nature; very few biological studies have been done. This group of water beetles and others related to it have suffered a number of name changes. The old family name Parnidae included the three sub­ families Psepheninae, Parninae, and Elminae. Leng (1920) raised each of these to family rank but designated Elmidae as Helmidae.

West (1929 b), in a study of larval anatomy, preserves the family name of Dryopidae and includes in it the subfamilies Psepheninae,

Dryopinae, and Elminae. Edwards (1949) retains Leng’s classifica­ ti o n .

The water penny P. herricki was originally discribed as a crustacean or as West (1929 b) states: "DeKay (1844) makes the unhappy blunder of describing the larva of Psephenus lecontei Lee, as a new species of crustacean Fluvicola herricki. the identity of which is finally set right by LeConte (1839, 1850),w The species

1181116 £ .* berricki takes priority over P. lecontei.

Few papers have been published on the biology of P. herricki.

Most of these consist of life history notes. Hubbard (1880) and

Leng (1894) were among the first to record short observations on the biology of this species. Matheson (1914) published the first major contribution on the life history of this insect. The only major publication since then is West’s (1929a) life history study.

Schafer (1950) contributed to our knowledge of this insect by providing additional information concerning life history and food habits. This study was part of a master's thesis but does not appear to have been published.

METHODS

P. herricki larvae are not restricted to any one given stream habitat and the abundance of larvae appeared to be in the form of a gradient decreasing from riffles to run areas. It was assumed that one factor or a combination of the various chemical, physical, or biotic factors in the streams could be shown to be responsible for effecting the habitat distribution of this species. It was then de­ cided to measure these factors on a quantitative comparative basis, e.g., how do these factors in a run habitat compare with those in the riffle habitat immediately downstream? Data were collected on these aspects of the problem at two permanent sampling stations on two different streams, the Olentangy River and Hayden Run. Samples were collected from the different habitats at each station on the same day if at all possible. It later became convenient to designate that part of the run immediately above the riffle as an intermediate zone. The reason for this will be discussed later. These permanent stations provided much of the quantitative data collected for this study, but many observations were also recorded from several different types of streams in and around central Ohio.

In this paper a riffle is defined as a relatively shallow portion of a stream where the water movement is of a turbulent flow.

The run areas are the deeper and quieter zones above and below the riffles. The water flow here is laminar. The zone designated as intermediate is actually part of the run just before the riffle break. The flow is smooth and laminar but the velocity is usually faster than in the upper parts of the run.

Sampling

Sampling Larval Populations

Quantitative sampling of larval populations was done with the use of the Surber Square Foot Bottom Sampler (Surber 1936). This sampler, or some modification of it, such as that devised by Hess

(1941), is in common use today and represents the only practical method for quantitative evaluation of stream bottom populations.

There are definite disadvantages inherent in this sampling method.

Proper use of the sampler for quantitative work lim its the sampling area to those portions of stream bottom where the water is shallow and the velocity relatively swift. Ordinarily, the sampler can be used effectively in areas up to 24 inches in depth and where the velocity is at least one foot per second. This limits its usage in most cases to stream riffle areas. Since the sampler only

covers a square foot area, it may be ineffective where there are many large boulders. The writer has also experienced difficulty in holding the sampler on the stream bed in certain riffles where the water velocity exceeds five feet per second. Needham and Usinger

(1956) also point out that it is difficult to avoid getting organisms

from outside the square foot frame, and that many organisms may

escape in swift water when back cufrents are created at the mouth of the net. It would be an understatement to say that sampling by this method is hard work. It is very tedious and time consuming and often unbearable under winter conditions as any experienced worker w ill testify. In spite of the many disadvantages, the Surber is widely used in aquatic work and is one of the few methods available for quantitative sampling of stream bottom populations.

The method ordinarily used in sampling with the Surber was modified somewhat for this study. Most population counts of water penny larvae were made directly in the field by picking the rocks from within the square foot frame of the sampler and looking at them closely under bright sunlight. The larvae were counted directly while on the rock and recorded as the number per square foot of bottom. The rocks with the larvae were placed back into the stream.

The depth to which the substrate was sampled depended on how deep the larvae could be found. Some samples were taken as deep as seven inches into the substrate. In certain areas, depending on population d e n s ity and th e ty p e o f s u b s tr a te , i t was n o t uncommon to spend one or two hours taking a single square foot sample. This method is tedious but fairly accurate if one is patient. At other times it was advantageous to collect all macroscopic organisms from the sampled areas to study the associations of animals. This was done by the ordinary Surber sampling procedure where the organisms were brushed off the rocks into the water, allowing the current to carry them into the net. The contents of the net were placed into pint jars containing 70 per cent alcohol and taken to the laboratory for sorting and identification.

It is well known that the Surber is usually used only in riffle areas and that sampling is dependent upon a good currentWith 6 organisms like water pennies, the Surber can be used as a quanti­ tative instrument in a variety of places. This is due to the morphology and behavior of the larvae. Water penny larvae are flat, highly streamlined and exhibit a very strong positive thigmotactic response. As a result, they can maintain their position on a rock in the swiftest current and are difficult to dislodge with the fingers or forceps. In vew of this, it must be mentioned that larval counts may not be accurate when deter­ mined by routine sampling procedures where the organisms are brushed off the rocks into the net. Owing to the form of the larvae and their ability to cling to a rock, the Surber sampler could be used essentially to close off a square foot space on the stream bottom. If the larvae do become dislodged they are helpless in the water and will drift with the current, no matter how slight, and become trapped in the net of the sampler.

The method stated above can be used to obtain accurate square foot counts of larvae from a wide variety of habitats. Current is not necessary to obtain quantitative data in comparing water penny populations from different habitats such as riffles, runs, or even shallow pool situations. Most sampling error results from the failure of the investigator to notice the smaller larvae. The larvae, upon hatching from the eggs, are tiny and colorless and cannot be seen or counted without a microscope. This results in con­ siderable error in estimating the numbers of larvae during the summer months. Slightly larger larvae, about two millimeters in length, are present most of the year, and the inexperienced collect- or may fail to notice these. This source of error can be elimi­ nated once the collector learns to "see" these small larvae.

Square foot bottom samples of larvae collected during this study

from riffle and run habitats do not necessarily give an approximation

of population size for that particular habitat. There are many utilizable microhabitats within any given area and the number of

samples required to estimate total numbers is too large to be practical. Needham and Usinger (1956) tried to determine the variability of the macrofauna of a single riffle in Prosser Creek,

California. One hundred Surber samples were collected from a 30 by 100 foot section of the riffle. Statistical analyses showed

that 73 samples were needed to give significant figures on total numbers at the 95 per cent level of confidence.

In the present study, quantitative larval counts were made with the idea of determining which habitat contained the most larvae but not n e c e s s a rily how many.

Chemical Analysis of Water

pH: The hydrogen ion concentration of the water was measured with a Beckman 180 portable pH meter. Most of the pH measurements were made directly in the field after the portable meter was stan­ dardized with a Beckman glass electrode model H-2 pH meter. On

several occasions, after measuring the pH of the water in the field,

samples of water were taken back to the laboratory and measured. The

time lapse from field measurement to laboratory determination was two hours and the pH did not change during this time. Several samples were later determined in the laboratory due to difficulty which developed in the portable meter. These readings were accepted as accurate on the basis of the above data.

Alkalinity: Total alkalinity of the water was determined in the field by the method outlined by Welch (1948) and is expressed as parts per million (p.p.m.) methyl orange alkalinity.

Dissolved Oxygen: Dissolved oxygen was measured by the un­ modified Winkler method (Welch 1948). All analyses were done in the field and most of the determinations were made during early after­ noon which probably represents the high for the day. One diurnal analysis was run during the summer when dissolved oxygen might prove to be a critical factor. Measurements were taken at dawn and at 2 P.M.

Free Carbon Dioxide: If the pH and total alkalinity of the water are known, free carbon dioxide can be found by the use of a graph showing the relation between total alkalinity, pH, and free carbon dioxide in natural waters (Dye 1944). Carbon dioxide is expressed in parts per million as calcium carbonate.

Physical Factors

Temperature: Water temperatures were measured to the nearest

0.5 F. with a three inch immersion Sargent thermometer and con­ verted to centigrade. The different habitats at each station were measured at the same time.

Velocity: Water velocity was measured with a pitot tube and surface floats. The pitot tube was used in the swifter parts of the stream and surface floats were used in the runs where the velocity was less than could be measured accurately by the pitot tube. The pitot tube was of the simplest design and constructed by bending ordinary glass tubing to an L-shaped design in a flame. The

following formula was used to determine water velocity:

V = 0.977 \j2gh" (1)

where Y equals velocity in feet per second; g equals 38.16 feet

per second; h equals the height of the water column in fractions of

a foot in the tube above the general water level; and 0.977 is a

c o n s ta n t.

Water velocity was measured one inch below the surface at the

sites from which samples were collected.

Depth and Width: Depth was measured with an ordinary rule at

the places where square foot samples were collected. Depth and width fluctuated considerably in the habitats at different times

depending on precipitation and the season of the year. Observations on depth and width were made with regard to these fluctuations so

that the relative changes in the habitats could be measured and

compared.

Turbidity: Routine turbidity readings of the water were taken by comparing water samples against silica standards. The results are

expressed as parts per million of silica. This was not accurate

enough for comparing the riffle and run habitats at a given station.

More accurate readings were obtained by measuring the light trans­ mittance of known silica standards in a Bausch and Lomb Spectronic

20 Colorimeter. A curve was plotted for these standards at a wave­ length of 400 millimicrons. Samples of water were then collected

from the various habitats at the same time and the per cent light

transmittance was measured with the colorimeter. These values were 10

then read from the curve as parts per million of silica.

Bottom Particles: Notes were taken on the size, shape, and arrangment of bottom particles each time a square foot sample was

collected. Wentworth (1922) designed a classification of coarser

sediments based on size of the particles. This classification is

in standard use in geology but does not appear to be completely

acceptable to all aquatic biologists. There is some confusion re­

garding bottom m aterial classification and no one system has become

standard. The term rubble is commonly used by biologists but does

not appear in Wentworth's system. The problem could be resolved

quite simply by adopting Wentworth's classification and adding the term rubble to mean a mixture of different types of bottom materials of various sizes and shapes. Such a classification has been adopted for the present study and is the same as that used by Stansberry

(1960).

Field data were recorded on the standard form illustrated in

F igure 1 . 11

n « id p»t» Bjmrt Cnrty. Ooli, Bo, Twnshj),_ ttao, : 3eotlon_ Station Local* _ Dr alms* Habitat __ Air T*Bp._ f s s n n r ■atar Taap, Light PH ____ ! fiaaolaMaiisd Blrith Daoth 02 Velocity 009 Weather AiiLninr

Velocity _ ?lants I articles Spaolaa Rich# ,

S&i fcwlw -gfaBL

Bisol. Botes On Bararoa

Fig. 1. Field data record card. 12

The Study Area

The importance of certain geologic and climatologic factors in relation to the distribution of P. herricki will be developed later in this paper. Thus, it seems advantageous at this point to describe the study area and briefly consider certain of these environmental components.

Climatology: Most of the streams studied are in central Ohio near the city of Columbus and can be seen on the Dublin, Ohio

Quadrangle, United States Geological Survey topographic map. Total precipitation for this area averages about 36 inches a year. Pre­ cipitation and temperature data for 1959 are given in Table 1. If one were to look simply at the annual averages for precipitation, he might assume that 1959 represents an average year. Actually, 1959 showed some very unusual departures from the average because freak weather occurred in January, May, June, August, and September. Heavy rainfall on January 20 and 21 produced floods in central Ohio and caused a state of national emergency in this area. The precipitation for May was close to the average but the distribution was very unusual. A flash flood occurred on May 30 in one of the streams con­ sidered in this study. The effects of this flood will be discussed later. The months of June, August, and September were exceptionally dry. June of 1959 was the driest June since 1930. A riffle in one of the study areas finally ceased to flow in September as a result of the dry summer. The w riter had not counted on this and was quite disturbed when it happened until he realized that this presented an 13

Table 1. Climatological Data for Columbus, Ohio, 1959

Month Precipitation D eparture Temp, D eparture

in inches from norm o F> from norm

January 7.44 4.5 0 26.0 -3 .7

February 3.08 0.81 32.7 1 .5

March 1 .4 5 -1 .9 8 38.8 -1 .0

April 3.60 0.16 52.6 2 .4

May 4.15 0.18 66.8 6.0

June 1 .5 5 -2 .7 8 71.5 0 .8

J u ly 3.2 3 -0 .6 2 75.4 1.0

August 1.5 5 -1.66 77.3 4.9

September 1.55 -1 .3 6 69.6 3.1

O ctober 3.3 3 1.15 55.1 0 .6

November 3.7 1 0.85 39.5 -2 .4

December 2.27 -0.22 36.4 4.7

T o ta ls 36.91 -0.97 53.8 17.9

(Source of data: United States Weather Bureau, Columbus, Ohio.) 14 unusual opportunity to study the survival of larvae under such conditions.

Hayden Gorge: Hayden Run is a small easterly flowing stream which enters the Scioto River at or near the Washington and Norwich

Township line in Franklin County, Ohio, about seven miles due north­ west of Columbus. This stream tumbles over a 30-foot limestone cliff forming Hayden Falls which is about 500 feet west of the Scioto River.

A narrow rocky gorge, 50 to 100 feet wide, extends from the falls east to the river. The flow of water along this gorge is highly variable.

During periods of normal precipitation, water cascades over the falls, producing a few deep pools and a long strech of rapidly flowing water.

There is always a small amount of water flowing down the gorge but after a week or two of drought, water no longer continues to flow over the falls. Some underground flow occurs in the valley floor as a re­ sult of water seepage into the gorge through the limestone strata.

The rocks of this gorge are Middle Devonian and were deposited in a shallow sea that covered the eastern, northern, and central parts of the state of Ohio. The rocks are composed entirely of Delaware and

Columbus limestone. The Columbus formation consists of a gray or brown massive and thin bedded limestone and chert. The Delaware for­ mation overlies the Columbus and is less than 18 feet thick and consists mostly of brown shale and black chert. The gorge itself has been cut into these rocks since the last retreat of Wisconsin ice in this area (Stauffer 1911).

About midway in the gorge is a riffle and run area which is fed 15 by a deep pool. These habitats were studied intensively during this research and are illustrated in Figures 6 and 7.

Olentangy River: Another permanent sampling station under study (during the spring and summer of 1959) is located on the

Olentangy River, one-half mile north of Worthington, Ohio. The bedrock here is the black Ohio shale but the stream bottom of the riffle and run habitats consists mostly of alluvium of limestone, shale, and glacial till.

Data were also collected from many habitats in several other streams in this area. Mill Creek enters the Scioto River at the village of Bellepoint. Bellepoint Run is directly across the river and enters the Scioto from the east. Both of these streams cut into the Columbus limestone and are located on the extreme north central section of the Dublin, Ohio quadrangle.

Observations were made in several places along Big Darby Creek southwest of Columbus. Scattered collections and observations were made in many other streams in the state but no detailed studies were done. 16

GEOGRAPHIC DISTRIBUTION

The geographic distribution of the genus Psephenus in

North America is given in Figure 2. Each mark on the map repre­ sents at least one county record. This data was assembled from published literature records and the following collections:

Illinois State Natural History Survey, Urbana, Illinois; The

United States National Museum, Washington 25, D.C.; Royal Ontario

Museum, 100 Queen's Park, Toronto 5, Canada; Canadian Department of Agriculture, Entomology Research Institute, Central Experimental

Farm, Ottawa, Canada; California Academy of Sciences, Golden Gate

Park, San Francisco 18, California; Department of Zoology and

Entomology, The Ohio State University, Columbus 10, Ohio; University of M ichigan, Museum o f Zoology, Ann A rbor, M ichigan; Frank N. Young,

Indiana University, Department of Zoology, Bloomington, Indiana;

Chad M. Murvosh, Department of Zoology and Entomology, The Ohio

State University, Columbus 10, Ohio; Paul Freytag, Department of

Zoology and Entomology, The Ohio State University, Columbus 10, Ohio.

The distribution of P. herricki is much more widespread than formerly reported. True, it is found in northeastern United States,

(Usinger 1956) and the northern and midwestern states, (Edwards

1949) but it has also been collected in Nova Scotia, New Brunswick,

Ottawa, Quebec, in most of southeastern United States, and as far west as Oklahoma and Texas. It has never been reported from Florida

(Young 1954, 1960). 17

The distribution of the western members of this genus appears restricted to California, Oregon, and Idaho. Muttkowski (1929) reports them as being rare in Yellowstone National Park. Psephenus has also been taken in southern Mexico and Brazil (Hinton 1934,

1937). There are specimens of this genus in the United States

National Museum from Trinidad, Uraguay, Tasmania, and Melbourne.

It is not known to occur in Europe. \

LEGEND! # Psephenus herricki APsephenus spp.

Fig. 2. The North American distribution of the genus Psephenus CD ECOLOGICAL LIFE HISTORY

Larvae

Description and Development

The anatomy of the larva of P. herricki has been adequately described and illustrated by several competent workers (Peterson

1957, Hinton 1939, West 1929 a, Schafer 1950, and K ellicott 1883).

There is no need to dwell at length on this point. Figure 3 is provided as a reference point for those unfamiliar with the general appearance of the larva.

Matheson (1914) estimated the length of the life cycle to be about one year. This estimate was based on field observations; no experimental rearing was done. West (1929 a) studied the life history and attempted to rear the larvae under laboratory condi­ tions. He concluded that the length of the life cycle was two years and that the larva was the overwintering stage. Schafer

(1950) believes that the entire life cycle is completed in 21 to 24 months. Her conclusions were based partly on field observations and partly on laboratory rearing. She tried to calculate the growth rate and the number of instars by measuring a series of specimens. These data on P. herricki, unfortunately, are not given in her paper. The number of instars has never been definitely established but it appears to be approximately six. Her rearing experiments indicate that larvae, upon hatching June 26, reach the third or fourth instar by September. Ho data are given as to the size of these instars. The young larvae overwinter and resume growth the following spring. If they reach maturity during this 20

season, they overwinter again and do not pupate until the follow­

ing spring or summer. Thus, two years are required for completion

of the life cycle. The two-year life cycle explains why both large

and small larvae can be found overwintering at the same time. In

fact, larvae of all sizes can be found throughout most of the year.

Figure 4 is a graph showing the number of larvae collected plotted

against the larval length in millimeters. All 116 larvae were

collected from the Hayden Gorge riffle on May 23, 1960. These larvae had overwintered from 1959 to 1960 and had fed for one month prior to being collected. Knowing that the first instar is 0.5 mm to 1.3 mm.

and the last Instar is 7 mm to 9 mm long, it would appear that there are six or seven instars. The exact number is still not known. The writer has made no direct attempt to determine this, although some rearing is presently being done to further elucidate the growth rate

of the larvae.

Molting: The new larval instar emerges through a long dorsal

slit which runs from the anterior end of the old larval skin to the first abdominal segment. The larva is almost colorless and appears white against a dark background. Tiny black dot markings are pre­

sent. The larva gradually turns brown during the next two or three d ays.

Rearing: It is easy to keep the larvae alive under laboratory conditions. All that is needed is a tank or vessel of some type which contains water and algae-coated rocks. The chlorinated tap water in Columbus, Ohio does not appear to be toxic. Agitation of the water is advisable to prevent stagnation but it is not necessary 'f o r '

WATER PENNY WATER PENNY

Fig. 3. The larva of P. herricki. 24

20 ■ -

1 5

10

"Hi—a.A- 3.S—3*—3^5—rc—ns—ru— 3 3 —o—kt 15 T3 B7B ' 970 Lmral length in m. Colicotad Hay 23, I960

Fig. 4. Total length measurements of viater penny larvae. 23 to bubble air or oxygen into the water. Rearing may be done in a small container or in an elaborate tank such as that used by the w riter, where part of a greenhouse bench was sealed off with concrete, filled with water, and covered by a large cage. An island area was provided in the center for pupation sites. A continuous flow of tap water was provided to simulate the constant flow of water in a stream. The excess water drains through an overflow pipe to a sewer. A variety of aquatic insects can be reared in such a tank.

Larval Food.

The best information on the food of the larvae is provided by

(Schafer 1950). This has never been published, thus it seems worth­ while to present it now in detail. In general, the food of the larvae consists of algae and microcrustaceans. No mention is made concerning types of microcrustaceans but the identified algae in­ clude th e fo llo w in g : (A) Diatoms - Gomphonema, N a v ic u la , N itz s c h ia ,

Synedra, Tabellaria, Asterionella and Cymbella; (B) Filamentous algae - Cladophora and Stigedonium; (C) Lesser abundant algae -

Cosmarium and Ohrococcus; and (D) Miscellaneous - sand and g rit and butterfly wing scales.

Gomphonema was the most abundant form taken from larvae collected in streams and Cymbella was the most abundant diatom in larvae collected in Lake Erie. Seventy-five larvae, collected from March 5 to June 20, were examined.

Winter Food: West (1929 a) found that the larvae do not feed during the winter. This conclusion was confirmed by results of the present study. No algae, grit, or food material of any kind could be found in the alimentary tracts of overwintering larvae collected on February 29 and April 5, 1960. Larvae collected

April 15, 1960, had their guts full of algae. Feeding by the larvae appears to be a function of their activity which, in turn, depends on the temperature of the water. They are very inactive during the winter months and appear to be in a quiescent state but w ill move slightly if exposed to bright sunlight and prodded with forceps. The larvae collected February 29 and April 5 responded in this way. The water temperature on February 29 was

2.2° C., and 7.7° C. on April 5. The weather in Columbus remained cold up to April 10 when a sudden period of very warm weather caused the temperature of the water to go up to 15.5° C. by April

15. This sudden rise in the water temperature was accompanied by a noticable increase in the activity of the larvae.

B ehavior

It was discovered quite early that the distribution of the larvae was often very spotty within a particular habitat. Several larvae might be found in one sample and none from an adjacent area a few inches to several feet away. Even within a square foot area, many of the larvae were usually taken from just a few rocks. It was also noticed that larvae were often very close together on the same rock which raised the question as to whether or not they were gregarious. An attempt to gain an insight into this unusual 25 microhabitat distribution resulted in laboratory experiments and field observations on the behavior of the larvae.

The first laboratory experiment was designed to find out how the larvae move in relation to the food supply. Sixty larvae of varying size were placed into a large galvanized wash tub which contained six large flat rough pieces of limestone rock. All of the rocks were about equal in size and shape and were collected from the stream in Hayden Gorge. Three of the rocks were treated with soap and water and sulfuric acid to remove all algae. They were then baked in a decontaminating oven for one hour at 300° 1., washed thoroughly in tap water and placed into the tub with the three untreated rocks. All of the rocks were placed on sand which covered the bottom of the container. Ninety-nine per cent of the larvae were found on the algae coated rocks 24 hours later. They were removed and placed on the algae free rocks but 77 per cent moved back to the algae-coated rocks within the next 24 hours.

This number increased to 79 per cent two days later.

An attempt was made to duplicate such an experiment under field conditions. An ideal situation was found at Bellepoint Run.

This tiny stream contains an abundant supply of larvae at a spot where the stream flows beneath a low, narrow, one-lane bridge.

The bridge is solid concrete and only six feet above the stream which results in heavy shading of that portion of the stream directly beneath the bridge. Other factors such as turbidity, pH, width, depth, velocity, bottom type, and water chemistry were measured to see if there were any differences between the shaded 26 and unshaded parts of the stream. None could be detected in a

15-foot section of the stream from beneath the bridge to several feet beyond. Quantitative bottom samples taken in these two zones should give some indication of the distribution of larvae in relation to the abundance of algae since all factors except light seemed to be equal.

The experiment was of short duration, unfortunately, because of a heavy rain which caused changes in depth, width, and velocity along the 15-foot experimental zone. Only two samples were collected prior to flooding. A square foot sample from beneath the bridge yielded 28 larvae as compared to 139 larvae taken in a square foot sample in the unshaded area. These are hardly enough quantitative data from which to base a conclusion but certain qualitative observations can be added. The larvae respond negatively to light and only come up on the tops of the rocks at night. Observations at night with a flashlight showed that there were more larvae on the tops of rocks near and beyond the margin of the bridge than directly beneath it. Random qualitative sampling during the day indicates the same thing. On the basis of both laboratory and field data, it seems logical to conclude that the microhabitat distribution of the larvae, depends to some extent, on the relative abundance and dis­ tribution of algae.

Phototropic Response: Negative phototropism was demonstrated in the laboratory by placing larvae in a long narrow (15" X 3") plastic container, one end of which was covered by a dark cloth, and the other end exposed to a source of bright light. All of the larvae 27 immediately migrated to the dark end of the container within a few minutes. Field observations confirm this. During daylight hours larvae are rarely found on the tops of rooks, but a few exceptions do occur. They have been noticed on the tops of rocks that were partly or completely shaded during late afternoon. This negative response to light is very strong in some larvae but weak in others. This can be detected in several ways. At night the weak radiation emitted by a flashlight will cause a few larvae to leave the top of a rock and crawl down beneath it but most larvae seem indifferent to this type of light. Also, if a rock is picked out of a stream and the larvae exposed to bright sunlight, they will crawl to the underside area of the stone, but some react much faster than others.

Thigmotactic Response: Detailed observations were made in the field and laboratory experiments were designed to determine if there was any relationship between size and shape of bottom parti­ cles and the distribution of water penny larvae. Mixed pebbles and small and large cobbles of various shapes were placed in a large container along with 90 larvae of varying size. The rocks were limestone and each was heavily coated with algae. The particles were placed on sand in the bottom of the container so that they could be removed, the larvae counted, and returned to their original position. The rocks were positioned such that each had lateral contact with two or three adjacent stones. Only three stones rested directly on top of three others. There was a total of 27 stones in 28 the container. The experiment ran for three weeks and data were collected weekly as to the number of larvae present on a particular rock.

The results are difficult to interpret because of the varying rock shapes. One fact, however, seemed evident. There appeared to be no relationship between the number of larvae on a particular rock and the size of that rock. This is supported by many detailed observations in the field. The size of a rock, as a factor in itself, is not important. In some cases, more larvae can be found on a larger rock than a smaller one but the reverse is often just as true. Very small pebbles (^" X ) have often been found with several larvae on them. Larvae have been found on rocks as small as five millimeters or as large as boulders but the size of the particle alone does not determine the number.

In the laboratory it was noticed that larvae were rarely found on any of the three rocks that laid loosely on tops of others. This raised the question that perhaps the position of one rock in rela­ tion to another was of some importance, and another experiment was designed to test this. Ten algae-coated rocks of about the same size and shape were put into a large galvanized wash tub which contained water and a sand bottom. The rocks were arranged in various ways in relation to the amount of contact they had with the substrate. Six of the rocks had little or no contact with the sand substrate, while the other four rested firmly on the sand. Seventy-seven larvae were distributed evenly throughout the container and counts made as to the number and distribution of larvae on the rocks. This experiment 29 was replicated four times during the week of May 4, 1959. The results are summarized in Table 2.

A total of 68 larvae were counted on the six rocks which had little or no contact with the sand substrate. The four rocks which were set firmly on the sand contained a total of 195 larvae or almost three times as many as the other six combined. It should be mentioned that most of the larvae found on rocks number 5 and 6 were always in the zone where the ends of the rocks came into contact with the sand.

The larvae of P. herrieki show a very strong positive thigmotactic response whereby they respond to a small tight niche such that both dorsal and ventral aspects of the body are in close contact with the material forming the substrate. This behavior seems to determine not only what rocks they may be found on but also the particular areas of those rocks. Carried still farther, it may explain why the microhabitat distribution is often spotty and account for field observations which indicate that the larvae are somewhat gregarious.

This idea is workable and can be used to some extent to predict the microhabitat distribution of larvae within a habitat. After a great deal of practice and observation, one can look at the rocks on a stream bottom and judge to some extent the type and amount of contact they have with other members of the substrate. Given a population of P. herricki larvae in the stream, it soon becomes easy to te ll which rocks they are most likely to be under. One soon develops a concept as to the type of niche in which the larvae are 30

Table 2. Relationship between the number of larvae on a rock and the relative position of the rock. The number of larvae are totaled for four experiments

Rock T o ta l Number

Number Rock Position o f Larvae

1 Very light bottom contact with sand. 22

2 No bottom contact with sand. 7

3 No bottom contact with sand. 0

4 No bottom contact with sand. 0

5 Ends of rock in contact with sand. 24

6 Ends of rock in contact with sand. 15

7 Rock bottom in firm contact with sand. 57

8 Rock bottom in firm contact with sand. 46

9 Rock bottom in firm contact with sand. 71

10 Rock bottom in firm contact with sand. 21 most likely found but this is rather difficult to define. In general it can be stated that the rocks must not be arranged too loosely or there may be few places where the larvae can wedga themselves into tight spots. On the other hand, however, the bottom materials should not be so densely packed together that all available niches are sealed tight. This type of arrangement occurs where the rocks are surrounded and packed together by very fine sand, silt, or clay.

Observations on certain other aquatic insects indicate that they have a similar type of behavior. This seems to be true with some hellgramites and adult aquatic beetles in the family Elmidae.

Elmids are most always found on those rocks where they can crawl into a very tight crevice. Two examples will serve to illustrate this behavior. The rocks in the Olentangy River are abundant with

Trichoptera larvae and their cases. The Elmid adults are always found in the tight crevices formed by the material that the

Trichoptera have accumulated and cemented together. The distribu­ tion of these beetles was noticed to be very spotty in another stream near Columbus. The bottom material of this stream is mostly very smooth rocks of shale and sandstone, with some granitic glacial outwash. A careful search along a one-half mile section of this stream revealed that the adult beetles were always on the underneath sides of the granite rocks and never on the sale or sandstone. The reason seemed to be that the shale and sandstone were perfectly smooth but the granite rocks were highly weathered 32 and deeply pitted. The beetles responded to these pitted areas on the rocks.

Ecological Distribution

The General Habitat: The habitat of the larvae has been described as clear, moderate to rapid streams with gravel or rocky bottoms (TJsinger 1956). Pennak (1953) describes the habitat as rocky or gravel bottoms along wave-swept shores and in streams where the water is shallow and swift. This is partly true. Actually, the larvae can be found in a wide variety of situations, from pools, runs, and riffles in many different types of streams, to certain ponds, springs, and lakeshores. It would even be incorrect to say that the larvae are restricted to water because there are certain situations when they can be found in moist places with little or no w a te r.

It has been mentioned that the numbers of P. herricki larvae occur in streams in the form of a gradient decreasing from riffles to run habitats. Quantitative square foot bottom samples show that riffles contain more larvae than any other type of stream habitat.

This has been found to be true in every stream examined. Quantita­ tive data for Hayden Gorge are presented in Figure 5. This graph shows striking differences as to the number of larvae in the different habitats. Samples collected from the intermediate zone show that it contains more larvae than the run just above but less than the riffle which breaks just a few feet below. The relation­ ships of these habitats to one another can be seen in the map Fig. 5. Graph of the relative numbers of P. herricki larvae in three habitats at Hayden Gorge. HUMBER

\ \ __ CP

J U M 1959 A U 1 1ST 19 5 9 35

HAYDEN GORGE STUDY AREA

IS" u*

Mi

O.0* Bspmd Rook W" Rktar Beptk ia „ JUt* DlraoUon it Velocity in Twt

Fig. 6. Map of the Hayden Gorge habitats showing some of the physical characteristics on May 23, 2A, I960. fa ta * 3 , G m x ssu s, c o ro m o re of habitus a t hashes goros s ro n r aioba. Bit* Habitat Diaaolrad Qtygan Frse Cp2 Total Alkalinity Eeter 98 Turbidity Tran.

i fa t. ppa. Ppa. o c ppa.

f/26/*9 m m * 8.00 88 2.3 265 20.6 8.35 0-10 2(00 R4U Zataraadiata 7.73 85 2.3 265 20.6 3.35 0-10 Hoi 7.55 83 2.3 265 20.6 8.35 0 - ID 6A9/&9 H iffl* 8.20 83 3.3 282 16.8 8.20 0-10 ®MB Zataraadiata 7.80 79 3.3 282 16.5 8.20 0 - 10 Rea 7.68 78 3.3 232 16.8 3.20 0-10 7/16/59 RiffI* 6.00 62 2.0 282 17.2 3.40 0-10 6(00 A A . Zataraadiata 5.60 58 2.0 282 17.2 8.40 0-10 Rob 5.60 58 2 JO 232 17.2 3.40 0 - 10 7/16/59 R iffls 8.80 96 2*2 312 20.C 3.40 0-10 2*00 PJ. Zataraadiata 3.00 85 2.2 312 18.9 3.40 0-10 Rob 8.00 85 2*2 312 18.9 3.40 0-10 9A l/*9 R im * Dry Dry Dry Dry. Dry Dry Dry Rb*a Zatanadiat* Dry Dry Dry Dry Dry Dry Dry Roa 8.80 88 6.5 372 15.5 8.00 2/29/60 R iffl* 13*40 98 2.1 270 2.2 3.35 0 - 5 3(30 F4U Zataraadiata 13*40 98 2.1 270 2.2 8.35 0 - 5 Raa 13.40 98 2.1 270 2.2 3.35 0 - 5 k / s r t / t o R im * 9.60 95 3.5 253 15.6 8.15 0 - 5 ?tOO P A Zataraadiata 9*28 93 3.5 251 15.6 3.15 0 - 5 Raa 9.28 93 3.5 253 15.6 3.15 0 - 5 shown in Figure 6. The inadequacy of the Surber sampling method has previously been discussed and the author has no intention of estimating larval population size based on this method. The re­ sults do show, however, that there are more larvae in one habitat than another. Every square foot sample in the riffle showed a high larval count except one which was relatively low, whereas every sample from the run yielded low numbers of larvae. The intermediate zone showed both high and low counts. The samples, taken from the intermediate gone, which gave high counts were collected just a few feet above the riffle. The numbers of larvae decreased as the distance from the riffle break increased.

Hayden Run is an unusual stream in that it has such an abundant population of larvae. Twenty-four samples were collected from the permanent sampling station on the Olentangy River during

April, May, June, and July of 1959 and the results are essentially the same. Most of the larvae occurred in the riffle. One larvae was found in the intermediate zone but none were collected in the run. P. herricki is less abundant in larger streams like the

Olentangy River and Big Darby Creek, but even so, their numbers decrease from riffle to run habitats. The larval distribution within the riffles of these streams is very unusual. Quantitative and qualitative samples from four different riffles on the Olentangy

River and four riffles on Big Darby Creek show that most of the larvae are found near the shore areas. Some light may be shed on 38 the problem of the habitat distribution of this species by examining the various environmental factors that are related to the problem.

Chemical Factors: The environmental faotors of the riffle,

Intermediate, and run habitats were measured at the same time so that comparisons could be made. A comparison of the chemical factors of the habitats at Hayden Gorge is given in Table 3.

These data present sufficient evidence that the chemical factors are practically identical between habitats hence have little or nothing to do with causing the larval distribution gradient in the habitats. The most variable condition exists in the amount of oxygen and it varies little from riffle to run at the same time on any given day. The greatest amount of variation in oxygen occurred at 2 P.M. July 16, 1959. The riffle was 96 per cent saturated as compared to 85 per cent for the intermediate and run habitats. In parts of oxygen per million parts of water, the difference was only

0.8 p.p.m. The temperature of the riffle was 1.1° 0. cooler than the other two habitats. At the other extreme, oxygen showed no variation at all on February 29, 1960. Data collected from the sampling station on the Olentangy River show the same results. The differences in the chemical factors between the riffle and run areas seem to be negligible.

Physical Factors: The map of the Hayden Gorge study area shown in Figure 6 illustrates some of the physical characteristics of the habitats during late spring. There are few differences between the riffle and intermediate zones during the winter and spring months. 39

The intermediate zone is wider and tends to be slightly deeper in the area near the run. There are many places in the inter­ mediate zone that are the same depth as the riffle. The velocity of the water is much the same this time of year but the intermediate lacks the turbulence of the riffle. The riffle becomes very shallow and slow moving during the summer but retains some of the tur­ bulence. The area south of the intermediate and run zones becomes dry during late spring and summer, the velocity of the intermediate zone decreases and it can no longer be distinguished from the run.

Water velocity, turbulence, and depth comprise the main differences between the riffle and run during most of the year. The run is several inches deeper but there are many places which are quite shallow. It appears that the only major difference between the riffle and run areas lies in the fact that the riffle has a more rapid and turbulent flow of water throughout most of the year but it is difficult to conceive that this alone is responsible as a cause of the larval distribution.

Turbidity, temperature, and size of bottom particles have been measured on a comparative basis and found to be very sim ilar.

Turbidity and temperature data for the habitats at Hayden Gorge are compared in Table 3. The visual method of measuring turbidity by comparing a water sample against a standard did not appear accurate enough for the purpose of this study thus, samples of water from the different habitats were brought into the laboratory and the per­ centage transmittance of light was measured by a colorimeter. The turbidity measurements of the riffle and run habitats for the spring and early summer of 1960 were found to be identical. The size of bottom particles is another factor that can be equalized and this is very unusual as compared with most stream bottoms. In many other streams, it is quite obvious that the riffles contain more and larger rocks than the run areas but this is not true for the three sampled habitats in Hayden Gorge. The physiographic nature of the gorge is such that erosion and deposition of the limestone rock has produced a rather homogenous bottom throughout the gorge.

In summary, it seems that the physical factors of velocity, turbulence, and depth are somehow responsible for the habitat dis­ tribution of the larvae of P. herricki since all other factors appear equal or nearly so. Shelford and Boesel (1942) studied the bottom animal communities of western Lake Erie and their data in­ dicate a correlation between depth and the distribution of larvae.

Most of the larvae were collected at depths of less than one meter and they were never taken below five and one half meters. Obser­ vations in central Ohio show that they do not occur in the deeper sections of the larger streams such as the mouth of Mill Creek which is normally flooded by a reservoir on the Scioto River, and the deep run sections of the Scioto River, the Olentangy River, and

Big Darby Creek. In some cases, they do not occur in the deep central parts of the riffles of these larger streams. Depth certainly appears to be important but depth, velocity, and tur­ bulence are interrelated factors of the environment. A more detailed discussion of this complex must await the development of additional data and w ill be treated at length later in this paper. Biotic Factors: The previous discussion on food indicated

that movements of the larvae may he regulated to some extent by

the distribution and abundance of algae. Those cases were very

unusual and it seems doubtful that larvae are often "hard pressed"

in finding food. The sampled habitats at Hayden Gorge contain an

abundance of algae; much more than the larvae could ever eat and

food does not appear important as a factor which would account for

their distribution in these habitats.

Information concerning the effects of predation on P. herricki larvae is scanty. A survey was made of the literature which con­ tained information on fish food and the stomach contents of various fish. Very few larvae have been found as a constituent of the

stomach contents of fish. West (1929 a) reports that water pennies

occur, very rarely, in the diet of the white sucker Catostomus

commersoni. The United States Fish and W ildlife Service is pre­

sently conducting a study of the fish food of certain species in the western end of Lake Erie. Ho water pennies have appeared in the

stomach contents of the following fish: spot-tail shiner, white bass, walleye, channel cat, sheepshead, yellow perch, emerald shiner,

gizzard shad, alewife, and trout perch (Price 1960). The United

States National Museum beetle collection contains a vial of two well

p reserv ed la rv a e th a t were tak en from tr o u t stom achs in Aukum,

California. These larvae represent one or more of the western mem­ bers of the genus Psephenus since P. herricki is not found in

California. On the basis of the available evidence, fish cannot be 42 considered as important predators of water penny larvae. Some of the riffle species, such as the darters, may feed on the larvae but more information is needed to verify this.

Other aquatic insects are potential predators of P. herricki but the data on this subject are almost non-existent. The writer has never observed, under field conditions, a single case of predation by other aquatic insects. Thousands of stones have been turned over and examined during this study with the hope of catching a predator in the act. Such was never the case. This, admittedly, is a poor way to study predation but it is one of the few available. The observer would have to literally crawl under the rocks to do such a study adequately. Considering the morphology of the larvae, e.g., the hard exoskeleton, the flattened streamlined shape and their ability to cling tightly to a rock, one has reason to doubt the effectiveness of small insect predators. This is further supported by the behavior of the larvae which enables them to move rather rapidly when disturbed and to crawl into very narrow niches.

The hellgrammite, Corydalus cornutus, has been observed to feed on water penny larvae under specialized laboratory conditions. Ten water penny larvae were placed in a wire cage containing a few stones and only one hellgrammite since they are cannibalistic. The cage was then submerged. All but three larvae were eaten within five days.

These three were then in turn eaten during the following twelve days.

The bodies of the larvae and most of the exoskeleton were consumed.

The very edges of the exoskeleton with the fine hairs were cast aside. 43

The only potential predators of any consequence living in the run habitat of Hayden Gorge are large numbers of the crayfishes

Gambarus bartoni and C_. rusticus, but it is rather doubtful that they have access to the tiny spaces in which the larvae of P. herricki l i v e .

Larvae from Hayden Gorge have not yet been examined for parasites, but a series of P. herricki larvae, collected from Lake

Brie, were examined by Dr. John Crites of The Ohio State University during the summer of 1959. No parasites could be found.

S u rv iv a l

The larva of P. herricki is a very hardy creature to say the least. Psephenid larvae collected from a stream and placed in a cork stoppered vial lived for a week without food or replenishment of the oxygen supply. Several other larvae were placed in a small metal container with little water and no food. It was the intention of the writer to put these larvae with others in the greenhouse, but the container became lost and forgotten among the maze of equipment on a workbench. Some of these larvae were still alive 18 days later; most of them died as a result of the formation of rust from the metal which became attached to the body of the larvae.

This species appears to have tremendous ecological tolerance.

The larvae can live in moist areas out of water for long periods of time. This has been demonstrated both in the field and laboratory.

A dozen larvae were put into a large galvanized tub containing only moist sand and a few algae-coated rocks. Water was added from time to time to keep the sand less than saturated. All of the larvae were 44 alive at the end of two weeks and the experiment was discontinued.

The larvae, under these conditions, appear to enter a quiescent state somewhat similar to their overwintering behavior. Field observations confirm that this ability to live in moist environ­ ments out of water has considerable survival value. The flow of water in the experimental riffle at Hayden Gorge ceased completely during September of 1959 due to the abnormally dry summer season.

This apparently had little or no effect on larval populations.

Four bottom samples taken the following May 23rd gave an average figure of 77 larvae per square foot of bottom. Almost all of these larvae were less than seven mm. long. Few mature larvae were en­ countered in the samples at this date because most of them had abandoned the riffle and moved to rocks along the shore-line close to future pupation sites. Thus, it appears that many of the larvae overwintered successfully in spite of the previous dry weather.

Several dry areas in the stream bed above the falls in Hayden

Gorge were also examined during the dry months of 1959. No dead larvae could be found. The larvae, apparently require only a thin film of moisture surrounding the gills for respiration to occur.

This enables them to survive in dry stream beds providing the sub­ strate is moist. Laboratory tests show that the larvae can only live for about two hours when they are placed into an environment that is completely dry. The riffle at Hayden Gorge is unique in that there is considerable moisture in the substrate even though the surface of the riffle becomes dry. The stream in Hayden Gorge is at a level almost equal to the Scioto River and as a result, the 45 water table lies just below the stream bed. The role of local physiographic conditions and how they relate to survival is now o b v io u s.

The ability of the larvae to survive in moist areas out of water is also important between the time interval that mature larvae leave the water and the beginning of pupation. Larvae may remain out of the water a week or more before pupating.

The effects of desiccation and low water have been discussed.

The only other physical factor of consequence to larval populations is flooding. Several observations have been made in regard to flooding and some quantitative data are available. Flash-flood conditions were created in Hayden Gorge as the result of very heavy rainfall on May 28, 29, and 30, 1959. The rocks in the stream bed were moved and shifted considerable by the force of the water. Many stones of cobble size were piled up in places where there were few or none before. The upper layer of rocks in the experimental riffle appeared to have been scoured away and dumped into the pool at the base of the riffle. Enough material was washed into this pool to reduce it’s depth by about two feet. After the flood, the rocks in the riffle appeared to be loose and looked as if someone had scrubbed them thoroughly with a wire brush. The rocks in the deeper run areas were also greatly disturbed and scoured of algae and sediment but not as much as the riffle. Figures 7, 8, and 9 show conditions at the riffle before, during, and after the flood. Note the grass growing on the bank on the far side of the riffle in

Figure 7. Now compare this with Figure 9. Most of the vegetation . 7. Habitats at Hayden Gorge before flood. 47

Fig. 8. Habitats at Hayden Gorge during flood. Fig. 9. Habitats at Hayden (Jorge after flood. 49 has disappeared. It was not washed away; it was covered by rocks deposited by the water. The top of this bank is about one foot higher than the normal water line.

The flood removed or destroyed most of the insect populations in the riffle. Very few mayflies, stoneflies, and caddisflies could be seen on June 1. Water pennies were the dominant form of insect life and they were still very abundant. One hundred six­ teen larvae were collected from a square foot bottom sample on

June 1. Most of these were less than seven mm. long; very few mature larvae were seen. Qualitative observations in the run and pool area below the riffle indicated that many of the larger larvae were washed out of the riffle. Large numbers of mature larvae had also left the riffle at this time to pupate on or near the shore.

The flood actually had little effect on the overall P. herricki populations. The water washed the top part of the riffle away but the smaller larvae, occurring deeper in the substrate, remained.

A light flash flood occurred at Bellepoint Run on May 26, 1960.

The water in this stream, rose suddenly within an hour, to a depth of two feet and the water velocity approached seven feet per second.

Normally, this stream is only two to three inches deep and the water trickles by at 0.5 foot per second or less. The writer could feel the rolling and shifting of bottom particles in the stream.

•Qualitative observations with a flashlight on the night of June 15 convinced this writer that the previous flood had little or no detrimental effect on larval populations because larvae were very 50 abundant and crawling everywhere about the tops of rocks. Many individual rocks contained 30 to 40 larvae each.

The force of flowing water itself is not enough to dislodge the streamlined larvae. They are able to cling tightly and crawl over the top of the rock in the swiftest current. The larvae can glide over the roughest type of rock without ever breaking the contact between the rock and the edge of the carapace. The grind­ ing action of rocks rolling in a swift current probably removes or even destroys some of the larger larvae. The smaller ones would escape this since they are able to crawl into the tiniest pits or crevices of any rock. They are also able to crawl deeper into the substrate where only the tiniest of niches occur.

P. herricki is usually thought of as being intolerant to pollution, being able to survive in only the cleanest waters. Various pollution studies, such as the one by Gaufin (1958) support this idea.

Although P. herricki is not normally found in water heavy with organic enrichment, they may be able to live in such waters. Larvae, put into wire cages containing algae-coated rocks, were able to survive in a polluted stream for over a month when the experiment was concluded.

This stream receives outfall from the H illiards, Ohio sewage disposal plant and empties into a reservoir on the Scioto River at Columbus, above Griggs Dam. The water is heavy with organic materials and detergents. The detergents often produce mounds of suds four to five feet high. It is very probable that P. herricki larvae cannot live in such water for two years and successfully pupate and emerge as fertile adults even though they are able to survive for short periods of time. It is also possible that some polluted waters are not toxic to many larval forms but that the obnoxious odor repels ovipositing adults. This idea merits considerable study, but is rarely mentioned in pollution studies. Pupae

Description

The pupa of P. herricki has been described and illustrated by

(Matheson 1914 and Schafer 1950). The length of the pupa is five

to eight millimeters. The initial color is white or light yellow

gradually turning to black. Eyes are present and black in color.

The pupa is very smooth and does not have any spines or setae. On

the latero-dorsal angles of the first abdominal segment are two

processes which are firmly attached to the lateral walls of the

last larval skin. It is under the covering of this last larval

skin that pupation occurs.

The length of the pupal stage appears to vary somewhat, but

this variation is slight. Schafer has established, on the basis of

laboratory rearing, that the pupal period lasts 10 to 11 days.

West (1929 a) states that the maximum time required for pupation is

12 d ays.

Ecological Distribution

Temporal: There is little or no information in the literature

that tells exactly when the pupa may be found. Matheson (1914) merely says that he found them on August 6. Schafer (1950) says

that the larvae leave the water in June and July and pupate.

Actually, pupation occurs throughout a large part of the summer.

The normal period for pupation begins toward the end of May and

extends into the summer to about the middle of August. The earliest

date for adult emergence in this part of Ohio has been found to be

June 5. Very few adults can be found at such an early date. This 53 suggests that May 23 is about as early as pupation occurs. Pupae are common the first week of June but few can be found prior to this d a te .

It is rather doubtful that any larvae pupate late in August.

An intensive search was made during the week of August 18, and none could be found except the remains of one dead adult that was in­ completely formed. Ovipositing adult females were found as late as

August 20. They were very few in number and this suggests that little or no pupation occurs past August 10.

Macronhabitat: In general, the macrohabitat of the pupae may be said to be those rocky shore areas several feet above the water line. Schafer (1950) found pupae attached to stones one to three feet above the water line. At Hayden Gorge, pupae could easily be found at a spot 5.5 feet away from the stream and on a slope that was about 10 inches higher than the water line and one cast skin was found 7.5 feet away from the water. Most of the pupae are usually found on the shore area one to three feet from the water.

It may be interesting at this time to make a comparison with the mexican form Psephenus palpalis Champ. Hinton (1939) reports that the pupa of P. palpalis is usually found within a few feet of the water line. They have, however, been found as far as 30 to 40 yards away from the nearest water.

Microhabitat: The pupae are usually found restricted to a definite type of niche within the given macrohabitat. This may be defined as that moist area on the underneath and side surfaces of rocks and logs which come into very close contact with some other 54

surface such as the soil or another stone. This appears to be a reflection of the behavior of the larvae as previously men­ tioned. It is this response that appears to determine more than

any other factor, how many larvae and pupae w ill be found on a particular surface. Size of the rock as a single factor is not

important. As many as half a dozen pupae have been observed on a tiny pebble one and one half inches long. Much larger rocks have been found with less pupae. The shape of the rocks is important, however, since this determines the alignment of one rock in rela­ tion to other surfaces. Gregariousness is another factor that may be important but is very difficult to measure and determine. The mature larva just before pupating, seems to be more gregarious than while it was living in the stream. Even when many suitable rock

surfaces are available, the mature larvae are much more numerous

on some rocks th a n on o th e rs .

S u rv iv al

The shore areas in which P. herricki pupates also harbors such

creatures as spiders, leeches, ants, and beetles. The only practical way to examine the effects of any possible predation is through ex­

amination of the last larval skin which covers the pupa. Any

predator would have to pierce or chew it's way through this pro­

tective covering to reach the pupa. The larval skin is firmly

attached to the rock forming a tight seal wherever it comes in con­

tact with the rock surface. This seal is strongest at the anal

region due to some adhesive substance which holds the pupa to the

ro c k . Many larval skins have been examined to evaluate the effects of predation and in most cases it appears that adult emergence is successful. It is unusual to find a larval skin that has been torn or damaged in any way. It may be that some predators will com­ pletely destroy or remove the pupa and the last larval skin thus, destroying the evidence. Such predation would go un-noticed. In general, it appears that pupal predation is very slight. This is probably due to the combined effects of the hard tight protective larval exoskeleton, and the shelter afforded by the unexposed areas in which the pupa is found.

Flooding appears to be the only physical agent of any consequence that may have harmful effects on pupal populations. Heavy rains such as that which occurred in Hayden Gorge May 28 and 29, 1959 resulted in swollen streams that overran areas in which the beetles were pupating. This could produce a high mortality of pupae if the streams remain high for several days. No quantitative data are available on this unfortunately. Some tests in the laboratory in­ dicate that pupae cannot survive long under water. A dozen pupae, that were submerged for 24 hours, were unable to complete develop­ ment. Psephenoides, an oriental genus, and some Eubrianax are the only members of the family able to pupate under water (Hinton 1939).

Pupation normally occurs in moist areas as has been mentioned.

Actually, successful emergence has been noted from a variety of substrate conditions ranging from soil and rocks that were very dry to areas that were saturated with water. 56

A d u lts

Adults of P. herricki are small flattened beetles, 4.5 to

6 mm. long. The color of the elytra varies from black to brownish.

Descriptions appear in the synopses published by LeConte (1852) and Horn (1870). Aside from genitalia, sex differences appear in the antennae and the color of the pronotum. The antennae of the females are nearly moniliform and the final segment not longer than the penultimate segment. The pronotum of the female is black and lacks luster. Males have sub-serrate antennae and the last joint is half again as long as the preceding one. The thorax of the male is less opaque than the female and is often shiny (Horn 1870). Figure

10 is a drawing showing the general appearance of the adult.

Ecological Distribution

The adults have been reported to emerge from June to September near Ithaca, New York (West 1929 a), and June to late August in the

Lake Erie region (Schafer 1950). Careful observations over two seasons indicate that they probably do not emerge in central Ohio before June. The first adult noticed in 1959 emerged in the lab­ oratory on June 3. A half-dozen beetles were seen in the Olentangy

River on June 9. No adults were found in Franklin County in 1960 until June 6. One emerged in the laboratory the previous night. In g e n e ra l, th e b e e tle s a re v ery uncommon th e f i r s t week o f June, and the collector w ill most likely miss them unless he is fam iliar with their habits. Newly formed adult beetles continue to emerge during most of the summer. Beetles are fairly common about the last half of

June and the population gradually increases to the middle or last 57

Fig. 10. An adult P. herricki. 58 part of July. The insects appear to be most abundant from about the middle of July to the first few weeks in August. The numbers decline rapidly after the middle of August and very few can be seen flying around the streams and landing on the rocks. A few females can be found laying eggs up to the last week in August.

The above statements are based mostly on qualitative field observa­ tions; very little quantitative data is available since there is no satisfactory method of sampling adult populations.

Both males and females emerge about the same time early in the season, and mating and oviposition occur immediately. The life span appears quite short. Schafer (1950) found that they lived in the laboratory from about two days to a week. The present study confirms this. The adults, according to West (1929 a), take little or no food. Schafer (1950) examined digestive tracts and found only small quantities of the unicellular algae Navicula and no other solid food. These algae are possible taken in when the adults drink.

The macrohabitat of the adults can be considered to be riffles or riffle-like areas in streams and along wave-swept shores of la k e s . The b e e tle s may f l y up and down th e stream s th e y in h a b it but only land on the stones exposed above the water line in riffles.

The microhabitat may be defined as those areas on the stones which are moist or wet as the result of being splashed by the turbulent flow of the water. 59

Behavior: The adults exhibit some very unusual and in­ teresting behavior patterns. The most complex and fascinating of these appears to be a peculiar mating ritual. This occurs above the water line on the stones in the riffles. The beetles are usually running very rapidly around the wet sides of these stones and appear to be very "excited.” Occasionally, two or more w ill bump or run into each other and become tangled up for a second or more. They separate and scurry off in different directions. This is repeated over and over. The beetles are constantly running into each other even on large rocks where there is ample room to move about. What appears to be attempts at copulation occur at this time. Most are unsuccessful. Very few copulating pairs have been seen during many hours of observation. Copulation was timed in only one pair and lasted seven seconds. At irregular intervals the beetles will stop running and stand motionless on the rock at the water's edge with the head end facing the water. The mouth parts appear to be immersed in the water at exactly the contact zone between the rock and the water. Beetles observed doing this in the laboratory produced only the slightest movement of the labial palps and appeared to be sucking up water. All of the adults on a single rock have been seen many times to line up at the same time in such a position and face the water. Fifty adults on a single boulder were once seen doing this. The beetles w ill then begin scurrying about the rock again, usually all at the same time. This behavior is repeated continously throughout the day. There are slight variations on this basic theme but the pattern is much the same. 60

This behavior does not seem to occur at night. Further study is needed on this phenomena to provide information on sex recognition and copulation success. It is well worth the interest of any

student of animal behavior. If one approaches the beetles slowly without making any sudden or jerky movement, he can move his head to within inches of the rock on which the beetles are active. Patience is necessary and the investigator must be prepared to sit down in the water and observe them for several hours.

Mating and oviposition seem to occur soon after emergence of the first beetles in June and takes place throughout the summer. Oviposi­

ting females can be found in late August, but their numbers diminish rapidly during the last half of that month. The females deposit eggs both during the day and night. Once one begins laying eggs, she will continue to do so, if undisturbed, and die shortly afterward without ever coming to the surface. The females enter the water from the rocks on which mating occurs and w ill climb down beneath that rock or one close by and lay the eggs in narrow rock niches. Ovipositing females seem to retain the positive thigmotactic response from the larval stage for they will crawl into very tight crevices and lay the eggs on the underneath sides of stones. One female was observed using her legs in a digging or burrowing fashion as she crawled down

into the sand a-longside of a small rock. Adult females appear to be

somewhat gregarious, for several are often found ovipositing in the

same area. As many as six females were once found together. The re­

sult is an egg mass of unusual size with two to four thousand eggs.

This gregariousness may be explained by the fact that females respond 61

to the same types of tight compact niches. Again, the position of

the rock and the niches created in relation to other members of bottom particles seems to be the important factor. Females w ill usually cease ovipositing on a rock that has been disturbed or re­ moved from the water. If the rock is replaced seemingly in the

same p o s itio n , th e y o fte n abandon i t and move to a n o th e r. As a result of this behavior, it has not been possible to observe

oviposition under natural conditions without destroying the micro­

habitat. The time required for laying an egg mass still needs to be determined. Females are quite docile during oviposition and can

easily be collected. They gradually become weak and die soon after

egg laying, probably as the result of the combined effects of

crawling into the bottom material and ovipositing without renewing

their air supply. The dense body hairs of the adult support a film

of air which surrounds the beetle thus, making underwater respira­

tion possible.

The adults of P. herricki are capable of very sudden and swift

flight. They take flight from a rock so quickly that the observer may begin to wonder whether he actually saw them. The beetles may

fly up and down the stream, just barely skimming the surface of the

water and alight on another rock just as quickly as they left. They

are extremely active during the day running about the rocks in the

riffle and flying from rock to rock. They can be approached with

caution and with practice, collected easily. At night they are re­

latively quiet and move about very little . They can usually be

found on wet leaves near or partially in the water or on the under­ side of stones which are not submerged but splashed by rippling water. The beetles are not in the water but olose to the rock- water contact zone. They are very still and may not move unless prodded. The beam from a flashlight does not stimulate them, in fact they w ill not respond to light at all at night, and attempts at collecting them in a light trap near the stream failed. They do not appear to have ever been collected in any light trap. The adults rarely, if ever, leave the stream to land on shore vegetation or venture overland.

The adults exhibit a very strong positive response to moist surfaces. This fact is demonstrated in several ways. The rocks on which the beetles are always found are those that are wave splashed by a turbulent flow of water and as a result are wet or moist all over. The writer has yet to observe them landing and running about a rock that was dry. Moreover, the beetles usually are found at the zone of contact between the rock and the water where the rock is very moist or wet. Some rocks in riffles have the top section dry and only the sides wet. Adults on these rocks usually restrict them­ selves to the wet sides and lee areas and rarely venture to the dry area. They may run over the dry area but never stay there. The rocks fitting the above description are ordinarily found only in riffle areas of streams or lake shores with wave action. Adults have never been seen to land on dry stones in run habitats or on shore.

Stones projecting above a run area are normally dry from the water surface up because the flow of water is laminar and rarely splashes th e s id e s . 63

This response to wet surfaces is shown in another way. The writer has observed and collected adults that landed either on his arms or the legs of his trousers. The only times that this has occurred was when the arms or pants became wet. This was checked several times by immersing that part of the arm up to the elbow.

The beetles flying about would never land on any part of the arm that was dry. This ability to spot a wet surface while in flight was demonstrated yet in another way. Several adults were being observed in a small riffle ten feet wide and about twenty feet long in a section of the Olentangy River. In this particular riffle, only three rocks broke the surface of the water and they were so wet as to be difficult to distinguish from other submerged rocks.

The writer disturbed the beetles on one of the rocks and they immediately took to the air but dove straight down and landed again on one of the other rocks. No other adults were on this rock.

This was repeated twice, and each time the beetles, in flight, unerringly picked out the rock barely exposed above water and flew straight to it.

The adults cannot swim and ordinarily never enter the water except to lay eggs (Schafer 1950). This is true for the most part but it should be added that adults on the sides of a gently sloping rock in a riffle sometimes run into the water but return immediately without submerging themselves. Once in a while water w ill splash over the top of a rock and wash the adults off. They quickly take to the air in such cases without really getting wet. The writer has been able to lift up rocks carefully with several beetles on 64 them and carry them to the swifter parts of a riffle and quickly submerge them. Sometimes the beetles fly upon contact with the water but often they remain clinging to the rock. Beetles were able to hang onto rocks in a current of 3.5 feet per second.

This was tried in a very swift rapids area of Big Darby Creek where the water was moving seven feet per second, but the beetles were washed off the rocks.

An interesting observation was made while attempting to photograph a single adult on a rock. A large fly, about twice the size of the beetle, was observed to land on this same rock six inches away from the beetle. The fly rushed toward the smaller insect as though it were going to "attack or fight" the beetle. When the fly was just a few millimeters away from the beetle, the psephenid began to flap i t ’s wings producing a rapid vibration. This seemed to cause the fly to leave the rock and take to the air but it landed again immediately. This time the beetle ran rapidly up to the fly and repeated the vibrating motion of the wings. This flapping of the wings near the face of the fly caused it to leave a second time; it did not return. 65

Eggs

Description and Development

The eggs of P. herricki have been described and illustrated by (Matheson 1914). The bright yellow eggs are deposited close together forming a mass and are held to the stone by a hyaline substance. Ordinarily, only a single layer of eggs is deposited; they are rarely piled on top of each other. The eggs are almost spherical but each is surrounded by a gelatinous material which results in a hexagonal outline. The diameter of the average egg is about 0.18 millimeter to 0.2 millimeter.

An attempt was made to determine the average number of eggs deposited by a single female after noticing that most of the egg masses were of approximately the same size. The size of the average egg mass appears to approach five by five millimeters or five by seven millimeters. There are usually 400 to 600 eggs in each mass with many of them containing nearly 500 eggs. A thousand or more eggs may be found in a single mass when two or more females oviposit close together.

The eggs hatch in 12 to 15 days (Schafer 1950). West (1929 a) found the minimum hatching time to be 12 days and that hatching of a complete egg mass takes place over a period of four days. Hatch­ ing has been observed during the present study. The young larva is colorless upon leaving the egg and cannot be seen with the naked eye. The length of the newly emerged larva is about 0.72 millimeters long and 0.44 millimeters wide. The bristles which surround the larvae are an added 0.16 millimeters.

i 66

Ecological Distribution

Macrohabitat: The habitat of the eggs is usually described as being on the underneath sides of stones in streams or lake shores where there is wave action. Chandler, in Usinger’s Aquatic

Insects of California, states: ’’The adults apparently deposit their eggs beneath the water on the face of stones which they can reach by crawling down from the surface. They are occasionally thus exposed when turning stones of which only the tops protrude from the water in midstream.” These statements are correct but only partly describe the true situation. It would be more correct to describe the general habitat or macrohabitat as riffles or riffle-like situations. Many observations in different types of streams confirm this. The eggs are always found in a habitat such as that produced in stream riffle areas. This does not necessarily imply rapid water flow areas alone but includes those places where water flow is turbulent but may still be relatively slow. This description of riffle conditions applies to those rocky lake shore areas where wave action produces a turbulent ebb and flow of water against the rocks. A rocky wave-swept beach may be considered a riffle for all practical purposes. Many of the ecological conditions are similar.

No eggs have ever been found in run or pool habitats of any of the smaller streams in central Ohio such as Hayden Run, Mill

Greek, or Big Darby Greek. They have never been found in any run areas of the Olentangy River. It is rather difficult to examine the quiet water areas of streams as large as the Scioto River and 67 other places such as the mouths of streams due to depth but some observations were made during the dry summer of 1959 when the water level in the two reservoirs on the Scioto River north of Columbus dropped considerably. Certain shallow areas in the river became accessible for observation and several hundred stones in a rocky area were examined in a futile effort to find either larvae or eggs. The mouth of Mill Creek is normally flooded when the upper reservoir is full of water but contained very little water during

August, 1959. A careful search was made along the rocky bottom of this stream for two-tenths of a mile. Mo eggs or larvae could be found. It should be mentioned that P. herricki is fairly abundant in the riffle areas of this stream three fourths of a mile above th e mouth.

Microhabitat: The microhabitat of the eggs may be defined as those areas within a riffle where wave splashed rocks project above the water line. These are the rocks on which the adults gather and from which the females enter the water and oviposit.

The eggs, however, are not necessarily laid beneath the rock by which the female enters the water. Upon reaching the bottom, she may wander around and lay her eggs on an adjacent rock that may or may not be covered by water or she may dig into the substrate and oviposit on rocks that are completely buried. The eggs are usually laid on the bottom or side areas of those rocks that come into close contact with other particles of the substrate.

It now seems quite clear that the location of the eggs is a direct result of the positive response of the adults to those 68 rocks that are kep wet by the action of turbulent water which laps the sides and occasionally breaks over the top. This explains why eggs are not found in run or pool habitats. Water flow in a run is often swift but the flow is laminar and the tops of rocks projecting out of water are very dry. The adults have never been seen to land on them.

In small shallow riffles such as the one in Hayden Gorge, rocks stick out of the water like many tiny islands during late spring and summer. Eggs, as a result, are distributed throughout the riffle. The situation will vary somewhat from stream to stream.

In riffles of larger streams such as Big Darby Creek and the

Olentangy River, eggs are rarely found in the center of the stream; they are limited to shore areas along the riffle. This is quite simple to explain from what is known about the behavior of the adults. The middle sections of these riffles often are deep and have few or no rocks sticking above the water line and the ovi­ positing females do not gain access to these sections of the stream. This is especially true of Big Darby Creek. Four riffles of this stream were carefully examined at different times and eggs could only be found near the shallow shore areas of the riffles.

The Olentangy River differs slightly. Riffle areas may be as deep as two feet in the center, but there is usually a shallow area where a few rocks stick out above the water line. Eggs have been found in such cases.

Temporal Distribution: The eggs of P. herricki can be found from June to late August (Schafer 1950). During 1959, no eggs 69

were found in Hayden Gorge until June 23. Oviposition probably

occurred before this date but was not discovered. Eggs are not

common early in June and the investigator may not see them unless

he is familiar with the niches in which they most likely may be

found. In 1960, oviposition first occurred on or near June 11.

Only two egg masses could be found on this early date. As more

adults emerge, egg production gradually increases from the middle

of June to the middle of July where it levels off and seems to remain about the same until about the end of July. The number of

egg masses gradually decreases during August. Very few were found

during the last week of August. One egg mass was found in Mill

Creek on September 8, 1959 and none were found after this date in

Hayden Gorge, Mill Creek, Bellepoint Hun, or Big Darby Creek.

Limited data are available concerning the number of eggs that may be found in a square-foot of bottom in a riffle. The

eggs in a sample from the Hayden Gorge riffle on July 16, 1959, were estimated to range in number from 72,000 to 120,000. On

August 20, 6100 eggs were estimated to have been deposited in a

square foot area. These calculations are based on the facts that

most egg masses are about the same size and that each contains

approximately 500 eggs. Measurements of the size of the egg

masses and the number of eggs in a mass were originally made in

the laboratory by using a dissecting microscope with a grid

e y ep iece. 70

Survival: The eggs, deposited as they are heneath stones in narrow niches, and often completely buried in the substrate, provide tremendous potential to success of the population as a whole. The large numbers of eggs deposited adds to this potential.

A very important factor, however, is the percentage of eggs that hatch. This can be determined either by gathering rocks with eggs that have completely hatched in the field and examining them in the laboratory, or collecting newly deposited eggs in the field and allowing them to hatch in the lab. An egg from which a larvae has successfully emerged can be seen under the microscope as a yellow shell with an emergence hole at the top. Examinations have been made by both of these procedures. The percentage of eggs that hatch is very high; counts indicate it to be above 90 per cent.

The eggs are not resistant to desiccation. Two masses of about 1000 eggs were taken out of water and allowed to desiccate for 24 hours under average room temperature and humidity condi­ tions. None of the eggs hatched. They begin to shrivel up and turn brown within a few hours after removal from the water.

Several rocks with egg masses were placed on top of a sponge that was immersed halfway in a tray of tap water in such a way that the eggs were kept constantly wet. Hatching was successful in every

case where the eggs were always in contact with the moisture. An egg mass on one of the rocks, however, was in a small pocket or

indentation of the rook. As a result, the eggs did not come into direct contact with the moisture on the sponge although the rock surface surrounding the egg was wet. These eggs turned brown and did not hatch.

There is no information on the effects of desiccation under field conditions but it seems that eggs are rarely subjected to such conditions. Although the water flow in a riffle may cease, the eggs would probably survive in a saturated zone in the sub­ strate. The amount of moisture within the substrate depends, of course, upon local physiographic conditions.

The effects of predation and parasitism, if any, are unknown.

Cannibalism, in this species, has never been observed, but this has not yet been checked experimentally in the laboratory. DISCUSSION

Habitat Distribution: There is on hand sufficient evidence to frame a hypothesis which explains the habitat distribution of

P. herricki. Several important factors are involved and they are closely interrelated which makes it difficult to say that any single one is the most important.

Eggs and adults are found primarily in riffles or riffle­ like places because of the behavior of the adults. Mating and oviposition occur only in riffle areas because the adult beetle responds strongly to those moist or wet rocks that project above the surface of the water. It was shown that riffles in larger streams, such as the Olentangy River and Big Darby Creek, rarely have any eggs, larvae, or adults of this species in the middle sections of the riffle because the water is deep enough to cover all the bottom materials and adult mating and oviposition are restricted to the shore areas of the riffles where wave-lapped rocks do project above the water line. Thus, the presence of adults and eggs in riffle habitats only, is a direct reflection of the behavior of the adult beetle. Evidence was presented earlier which showed that adults or eggs are rarely found outside the riffle habitat. The only exception to this was the presence of two or three egg masses found in the intermediate zone. This intermediate zone, several feet above the riffle break, can be considered a run for all practical purposes but occasionally takes on the aspects of a riffle. This varies considerably with the amount of precipitation and the season of the year. A shallow

72 intermediate area, with rocks sticking above the water-line,

could easily be transformed into a riffle for a short period of time following a heavy rain. If this occurred during the summer months, some oviposition would probably occur in this habitat.

The habitat of the larvae can be considered to be riffles for they occur there in the greatest abundance. They can also be

found in other habitats but this varies with local physiographic

conditions. In Hayden Gorge, the larvae are fairly common in the run but are absent from or rarely occur in the runs of larger streams. The relative abundance of larvae in riffles is due to adult oviposition and egg hatch in this habitat and the fact that larval movement is somewhat restricted for they do not move great distances from the places where egg hatching occurs. This is demonstrated by their absence from most run habitats and the middle sections of deep riffles. Larvae are not found in the deep sections of some of the riffles of Big Darby Creek because mating and oviposition occur along the shallow shore areas and the larvae, upon hatching, do not venture far from these areas.

The larvae are capable of considerable movement, at times, especially during the spring and summer, when they migrate quite a distance and may climb up on the banks and pupate. This raises a problem and proposes the question: Why don't the larvae move out of riffle areas and become dispersed throughout the entire length of the stream in the course of two years? The answer to this problem lies in a thorough understanding of the relationship of the behavior of the larvae to it's microhabitat. 74

Laboratory experiments and field observations have shown that the larvae respond very strongly to tiny niches in which they can become tightly wedged among the bottom particles. Other factors being equal, this thigmotactic response determines to a great extent not only on what rocks the larvae may be found but also the particular parts of that rock. The relative position and arrangement of bottom particles in a stream and the abundance and diversity of niches created is undoubtedly important in regard to the microhabitat distribution of other aquatic insects.

B ritt (1955) touched upon this subject when he said: "I have observed that the position of a stone on the bottom, that is, whether the stone is pressed into: the bottom or is held up by other stones so that water currents pass under it, greatly in­ fluences the size of the animal population inhabiting the stone."

The size of bottom particles alone does not appear important in governing the habitat distribution of the larvae because of the relative homogeneity of the bottom materials in the riffle, intermediate, and run habitats at Hayden Gorge. A closer look at the bottom materials, however, reveals a striking difference in the arrangement of the rocks. The various materials in the riffle bottom are much more compact than those of the run, especially the top layer of rocks. Differences other than arrangement can be detected. The depth to which a sample can be taken is much greater in the riffle e.g., the larvae of P. herricki, as well as other in­ sects, occur at greater depths in the substrate of the riffle than the run. This is because the bottom particles are relatively free 75 of tiny particles that cement or seal off all available spaces.

One has to sample to a depth of three to six inches into the riffle substrate at Hayden Gorge before compaction of sediments is encountered. The run substrate, however, is very tight and compact one to two inches below the top layer of rocks, which re­ sults in sealing off the available spaces at less depth. Algae is less abundant in the run as compared to the riffle. Superfi­ cially, there appears to be as much algae in the bottom of the run as there is in the riffle but this is due to a heavy coating of algae on the surface of the top layers of rocks. The under­ neath surfaces of the top layer of rocks is almost void of algae and the algae decrease rapidly as the depth of the substrate increases. This is in contrast to the riffle where algae not only occurs at a greater depth in the substrate but is also more abundant on the lower surfaces of the top layer of bottom materials.

The greater number and diversity of available microhabitats in the Hayden Gorge riffle must be dependent on turbulence and velocity because these are the only outstanding differences be­ tween the riffle and run habitats. Water chemistry is certainly important to biological productivity in general, but an ex­ planation of the distribution of water penny larvae cannot be found here because there was little or no difference in the water chemistry of the sampled habitats. Turbidity, temperature, pH, and size of bottom materials were found to be identical or sim ilar. Even depth was found not to differ markedly between the riffle and the intermediate areas although the run was somewhat deeper. The outstanding differences were found to occur with velocity and turbulence and arrangement of bottom m aterials. The arrangement, of course, is partially dependent on size and 3hape.

Water velocity alone cannot be responsible for the microhabitat differences between the riffle and run because water movement can often be quite swift without having a pronounced effect on the bottom. It is not laminar flow but the turbulent flow of the water that is primarily responsible for re-working the bottom materials in a riffle. This physical effect produces such an arrangement of the materials, that a greater number of available niches are formed in the spaces among the rocks. Turbulence pre­ vents the accumulation of very fine silt and sand which would clog the upper portions of the substrate. Too much of this results in a hardpan-like material and is detrimental, but the writer has also observed that a small amount of sand material clinging to a rock may somehow influence the accumulation of large numbers of organisms on that rock. Turbulence also moves and shifts the bottom materials causing a greater number of rock surfaces to be exposed to sunlight thus, effecting greater algal growth. Added to this is the probable filtration of plankton through the action of turbulence on the bottom m aterials. McFadden (1954) observed that rock debris may act as a filter causing decrease in plankton within short distances.

Turbulence and velocity are important not only in the creation of larval microhabitats but are also directly responsible for producing the moist or wet adult habitats on rocks projecting above 77 the water line in a riffle. M ult beetles respond to this type of surface, mate, enter the water and oviposit nearby. Again, velocity alone could not produce the proper conditions; turbulent flow is needed.

The hypothesis is hereby advanced that the habitat distribution of the water penny P. herricki is primarily a function of water turbulence. Turbulence appears to be the most dominant factor since it directly causes a chain of events that affect the distribution of most of the life stages of the water penny. One cannot, however, divorce turbulence from other interrelated variables and remain within the realm of ecology. Turbulence, velocity, and depth are intimately connected and these are directly related to local physiographic and climatic conditions. Depth does not appear im­ portant until one considers the absence of adults and eggs, or the reduction or absence of larvae from the middle sections of large riffles, which are deep enough to completely cover all bottom particles, cutting off adult access to that part of the riffle.

The relationship between biotic and physical factors becomes apparent when one considers the relative importance of adult and larval be­ havior to the micro-environments created by the physical agents.

It is opportune at this time to carry the discussion one step farther and approach the problem of the relative abundance of in­ sects in riffles as compared to other types of stream habitats.

The evidence from several investigations indicates that riffles are the most productive type of habitat (Sprules 1947, Pennak and Van

Gerpen 1947), and that there is a relationship between standing 78

crop and the type of bottom. Standing crop appears to decrease in the order: plant beds, large rubble riffle, mixed rubble, medium rubble, small rubble, gravel, muck, sand, and bedrock (Needham 1927,

Linduska 1942, Sprules 1947). This problem is thoroughly reviewed

in an excellent discussion by Sprules (1947) who postulates that there is a direct relationship between the utilizable surface area of bottom particles exposed to the water and the productivity of aquatic insects. The present study substantiates this hypothesis.

The idea that there is more living space in a riffle does not solve the problem; it proposes another "why?''. The various studies associated with this problem have placed emphasis on different factors, mostly current and bottom type. Although turbulence is an

integral part of current, it has not received much attention in the literature. The problem of riffle productivity is difficult be­

cause of the many variables, most of which affect each other. The situation at Hayden Gorge is unique in that many of the factors of the riffle and run habitats are similar if not identical, and enables this problem to be examined on an experimental level. The discussion in the previous section upholds the idea that there is more living space because of more and diverse microhabitats within the riffle bottom, and proposes that these are created by the

combined effects of several factors, of which turbulence appears dom inant.

Dispersal: Movements of the larvae are restricted for the most part and their dispersion from a particular habitat or stream to another is probably an uncommon event. The adults are very active 79 and swift fliers and must be the key agents in dispersal. They rarely live more than a week, however, and their behavior would appear to restrict them to the stream valley in which they emerged, but the wide distribution of this species is evidence that enough dispersion occurs to prevent population isolation. A crude figure of dispersal power can be obtained by calculating how fast the species spread north after the last retreat of ice.

P. herricki has been collected west of Ottawa, Ontario near la ti­ tude 45.5°. Recent radiocarbon dates indicate that deglaciation and opening of the North Bay outlet near latitude 46° occurred about 10,000 years ago (Terasmae and Hughes 1960). How far south the species was forced or how rapidly they moved northward in front of the ice sheet is unknown. It is known that the last ice left northern Ohio 13,000 to 14,000 years ago. The beetle popu­ lation may have advanced rapidly in front of the retreating ice but this is doubtful, and on the basis of the present evidence, the maximum time for dispersal of the population northward into southern Canada is about 10,000 years. This, of course, is based on the assumption that the species today is the same as that which ex­ isted several thousand years ago. Evolutionary change and dispersal of the fauna in time is unknown except for the fossil j?. lutulentus, which has been recorded from the I’lorissant of Colorado (Scudder

1900).

Information is needed about barriers to dispersal. The dis­ tribution pattern and the wide separation of eastern and western members of the genus suggests that the Great Plains and the 80

Rocky Mountains act as a barrier. If this is true, the reason may

lie in the physical nature of the streams of the plains and or may

be complicated by other factors such as altitude, but one can only

speculate at present.

Population Abundance: The available data indicate a correlation

between population abundance and stream size. In general, smaller

tributaries appear to have greater numbers of individuals per habitat

or per unit area within the habitat than larger streams. The reasons

for this are not thoroughly understood but part of the answer seems

to lie in the differences among the physical conditions of the

streams and the number and variety of habitats created by these

physical factors. A comparison of the chemical factors of the

streams around Columbus reveals that they are quite similar; the main differences exist among temperature, turbidity, velocity and

turbulence, depth, bottom type, and width. The influence of biotic

factors on population abundance is unknown and proposes an interest­

ing and challenging problem. SUMMARY

An ecological study of the water penny Psephenus herricki

(DeKay) was made in an attempt to describe and explain the macrohabitat and microhabitat distribution of the various life stages of this insect. Observations and experiments were con­ ducted both in the laboratory and in various streams around central Ohio. Qualitative and quantitative sampling showed that the larvae are more abundant in riffles than in any other type of stream habitat. Observations on the mating and oviposition be­ havior of the adults showed that this behavior occurs only in riffle areas because the adults respond positively only to those moist or wet rocks sticking above the water line in riffles.

The turbulent flow of water is responsible for creating this type of habitat.

Studies on the behavior of the larvae and the microhabitats within a stream bottom indicate that there are many more suitable larval niches within a riffle than in other types of stream habi­ tats. The larva exhibits a very strong positive thigmotactic response and rarely leaves these niches. This abundance of niches within a riffle is due to the interaction of several agents e.g., velocity and turbulence, depth, and arrangement of bottom particles, but the dominant factor appears to be water tur- belence which continually re-works the bottom m aterials. This produces an arrangement of particles resulting in a greater number of larval niches. Turbulence appeared to be such an important

81 factor influencing the distribution of most of the life stages of this species, that it was hypothesized that the habitat distribu­ tion of this species is primarily a function of turbulence. The relative importance of other physical factors is also discussed at length. Water chemistry and many of the physical factors are dis­ missed as important agents because they were sim ilar or equal in the habitats studied.

Data are presented concerning the effects of physical and biological factors to survival of populations. Additional life history observations have been recorded to supplement existing information. The geographic distribution is given and shown to be greater than previously reported. LITERATURE CITED

Borror, D.J., and D.M. DeLong. An introduction to the study of insects. New York, N.Y.: Rinehart and Co. 1030 p.

B ritt, N. Wilson. 1955. New methods of collecting bottom fauna from shoals or rubble bottoms of lakes and streams. Ecology 36: 524-525.

DeKay, J.E. 1844. Zoology of New York, or the New York fauna. Part VI Crustacea. Albany, N.Y.: Carroll and Cook. 65 p.

Dye, J.F. 1944. The calculation of alkalinities and free carbon dioxide in water by the use of nomographs. Jour. Amer. Water Works Association 36: 895-900.

Edwards, J.C. 1949. Coleoptera or beetles east of the great plains. Ann Arbor, Mich.: Edwards Bros. Inc. 181 p.

Gaufin, A.R. 1958. The effects of pollution on a midwestern stream. Ohio Jour. Sci. 58: 197-208.

Hess, A.D. 1941. New limnological sampling equipment. Limnol. Soc. Amer., Spec. Pub. No. 6.

Hinton, H.E. 1934. Psephenus usingeri, fc. sp. from Mexico with notes on the regional Ps. palpalis (Coleoptera: Psephenidae). Ann. Ent. Soc. Amer. 27: 616-618.

______. 1937. On the Psephenidae collected by Dr. Eritz Plaumann in Brazil (Coleoptera). Proc. Royal Ent. Soc. London. Series B. Taxonomy. 6: 9-13.

______. 1939. An inquiry into the natural classification of the Dryopoidea, based partly on a study of their internal anatomy (Coleoptera). Trans. Royal Ent. Soc. London. 89: 133-184.

. 1955. On the respiratory adaptations, biology, and taxonomy of the Psephenidae, with notes on some related families (Coleoptera). Proc. Zool. Soc. London. 125: 543- 568.

Horn, G.H. 1870. Synopsis of the Parnidae of the United States. Trans. Amer. Ent. Soc. 3: 29-42.

Hubbard, H.G. 1880. Habits of Psephenus lecontei Lee. The Amer. Entomologist 3:73.

83 84

Kellicott, D.S. 1883. Psephenus lecontei. On the external anatomy of the larva. Can. Ent. 15: 191-196.

LeConte, J.L. 1849. On the metamorphosis of Fluvicola herricki. Proc. Amer. Ass. Adv. Sci. 2: 272.

______1850. (Description of larva and pupa of Psephenus lecontei). In Agassiz* Lake Superior, pp. 241-242.

______1852. Synopsis of the Parnidae of the United States. Proc. Acad. Nat. Sci. Phil. 6: 41-44.

Leng, C.W. 1894. Notes on Psephenus lecontei Lee. Jour. N.Y. Ent. Soo. 2: 86.

______1920. Catalogue of the Coleoptera of America north of Mexico. Mount Vernon, N.Y.: John D. Sherman. 470 p.

Linduska, J. P. 1942. Bottom type as a factor influencing the local distribution of mayfly nymphs. Can. Ent. 74: 26-30.

Matheson, R. 1914. Life history notes on two Coleoptera (Parnidae) Can. Ent. 46: 185-189.

McFadden, J.T. 1954. Population fluctuations in the plankton of O'Shaughnessy Reservoir and in the Scioto River below the dam. Master of Science thesis. The Ohio State University, Columbus. 57 p.

Muttkowski, R.A. 1929. The ecology of trout streams in Yellowstone Natl. Park. Bull. N.Y. State Coll. Forestry, Syracuse Univ., Roosevelt W ildlife Annals 2: 151-240.

Needham, P.R. 1934. Quantitative studies of stream bottom foods. Trans. Amer. Fish. Soc. 64: 238-247.

______, and R.L. Usinger. 1956. Variability in the macro­ fauna of a single riffle in Prosser Creek, California, as indicated by the Surber sampler. Hilgardia 24: 383-409.

Pennak, R.W. 1953. Fresh water invertebrates of the United States. N.Y.: Ronald Press Co. 769 p.

, and E.D. Van Gerpen. 1947. Bottom fauna production and physical nature of the substrate in a northern Colorado trout stream. Ecology 28: 42-48.

Peterson, Alvabu 1957. Larvae of Insects. Part II. Ann Arbor, Mich.: Edwards Bros. Inc. 416 p. 85

Price, John W. 1959. The Ohio State University Research Founda­ tion Report -837-Final. June 16, 1958-Sept. 15, 1959. United States Fish and W ildlife Service Contract no. 14-17-008-56.

Schafer, Katherine Ann. 1950. Life history studies of Psephenus lecontei Lee. and Ectopria nervosa Melsh. (Coleoptera: Psephenidae; Dascillidae) Master of Science thesis. The Ohio State University, Columbus. 51 p.

Scudder, S.H. 1900. Adephagous and Clavicorn Coleoptera from the Tertiary Deposits at Florissant, Colorado with descriptions of a few other forms and a systematic list of the non- rhynchophorous Tertiary Coleoptera of North America. U.S. G eological Survey Monographs XL. 117 p .

Shelford, V.E., and M.W. Boesel. 1942. Bottom animal communities of the island area of western Lake Erie in the summer of 1937. Ohio Jour. Sci. 42: 179-190.

Sprules, W.M. 1947. An ecologioal investigation of stream insects in Algonquin Park, Ontario. Univ. Toronto Studies Biol. Series. No. 56. Pub. Ontario Fish. Res. Lab. LXEX. 81 p.

Stansberry, D.H. 1960. The Unioninae (Mollusca, Pelecypoda, Naiadacaa) of Fishery Bay, South Bass Island, Lake Erie. Ph. D. thesi3. The Ohio State University, Columbus. 216 p.

Stauffer, C.R., G.D. Hubbard, and J.A. Bownocker. 1911. Geology of the Columbus quadrangle. Geol. Survey Ohio. Fourth Series, Bull. 14.

Surber, E.W. 1937. Rainbow trout and bottom fauna production in one mile of stream. Trans. Amer. Fish. Soc. 66: 193-202.

Terasmae, J., and O.L. Hughes. I960*Glacial retreat in the North Bay area, Ontario. Science 131: 1444-1446.

Usinger, R.L., et. al. 1956. Aquatic Insects of California with keys to North American genera and California species. Berkeley, Calif.: Univ. of Calif. Press. 488 p.

Welch, P.S. 1948. Linnologieal Methods. Philadelphia, Pa.: Blakiston. 381 p.

Wentworth, O.K. 1922. A scale of grade and class terms for clastic sediments. Jour. Geol. 30: 377-392. West, Luther S. 1929 a. Life history notes on Psephenus lecontei Lee. (Coleoptera; Dryopoidea; Psephenidae.1 Battle Creek College Bull. 3: 3-20

______1929 b. A preliminary study of larval structure in the Dryopidae. Ann. Ent. Soc. Amer. 22: 691-727.

Young, F.N. 1954. The water beetles of Florida. Univ. Florida Studies Biol. Sci. Ser. 5.

______1960. Personal communication. AUTOBIOGRAPHY

I, Chad Michael Murvosh, was born in Toronto, Ohio, August 10,

1931. I received my secondary school education in the public

schools of that city, and my undergraduate training at Kent State

University, Kent, Ohio, which granted me the Bachelor of Science

degree in 1953. My education was interrupted for two years during which time I served in the United States Army Medical Corps. I

entered The Ohio State University in 1956 and received the Master

of Science degree in 1958. While in residence at The Ohio State

University, I acted in the capacity of Graduate Assistant in the

Department of Zoology and Entomology from 1956 to 1960.

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