This dissertation has been 61-5077 microfilmed exactly as received

CURRIE, Neva Louise, 1934- STUDIES OF THE BIOLOGY OF ERYTHEMIS SIMP LICICO LLIS (SAY) (ODONATA: LIBEL- LULIDAE.

The Ohio State University, Ph.D., 1961 Zoology

University Microfilms, Inc., Ann Arbor, Michigan STUDIES OF THE BIOLOGY OF ERYTHEMIS SIMPLICICOLLIS (SAY)

(ODONATA;LIBELLULIDAE)

DISSERTATION

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

By

NEVA LOUISE CURRIE, B.A., M.Sc.

*******

The Ohio State University

1961

Approved hy

HHiwiAV — — uim Entomology ACKNOWLEDGMENTS

I wish to express my appreciation to my adviser,

Dr. Donald J. Borror, for his suggestions, assistance, and advice throughout this study and in the preparation of this manuscript. I also wish to thank the staff of the Delaware

Reservoir Wildlife Area for information regarding the field area and for the loan of aerial photographs of the part in which this study was centered. Finally I want to express my gratitude to the Graduate School of The Ohio State University and to the National Science Foundation for fellowships which made this study possible.

ii TABLE OF COMTEHTS

Page

IHTRODUCTION ...... 1

METHODS OF STUDY ...... -...... 3

The Field A r e a ...... 3 The Species Studied ...... 9 Field Work . 11 Marking Adults ...... 12

THE A D U L T ...... 19

Emergence . . ~ 7 ...... 19 Seasonal Distribution of Emergence ...... 21 Maturation Period . 25 C o l o r a t i o n...... 25 Behavior and Movements ...... 32 Reproductive Period of Males ...... 36 Intermediate Males at Ponds ...... 36 Movements to P o n & s ...... 38 Movements from Ponds to Areas Away from Ponds . 43 Movements Between Areas Away from Ponds .... 43 Behavior at Ponds ...... 45 Localization ...... 53 Reproductive Period of Females ...... 56 Hon-pruinose Females at Ponds ...... 56 Movements toPonds .... 56 Movements from Ponds to Areas Away from Ponds . 59 Movements Between Areas Away from Ponds .... 59 Localization ...... 6l Mating ...... 63 Oviposition ...... 65 Repetition of Oviposition ...... 68 Sex Ratio ...... 69 Length of Adult L i f e ...... 70 Food of A d u l t s ...... 70 Enemies of Adults ...... 73 P r e d a t o r s ...... 73 Weather and Injuries ...... 75 P a r a s i t e s ...... 77 Recovery of Marked Individuals ...... 80

iii TABLE OF CONTENTS— (Continued)

Page

THE N Y M P H ...... 82

Food of N y m p h s ...... 82 P r e d a t o r s ...... 83 Duration of theNymphal Pe r i o d ...... 84

DISCUSSION ...... 88

Dispersal ...... 88 Functions of Some Aspects ofBe h a v i o r ...... 89 Territorialism ...... 91

SUMMARY ...... 94

LITERATURE CITED ...... 98

iv LIST OF TABLES

Table Page

1 Marking and recovery summary ...... 17

2 Single and multiple recoveries ...... 18

3 Time elapsed during stages of emergence .... 20

4 Color patterns of individuals marked on day of e m e r g e n c e ...... 26

5 Repeated observations of individuals, in areas 1 to 10, during the maturation period . . . 35

6 Total records of males (number marked plus total recoveries) ...... 37

7 Observations of some intermediate males at ponds 39

8 Movements of males to ponds ...... 40

9 Movements of males to ponds 36 and 3 7 ...... 41

10 Movements of males between areas away from ponds 44

11 Records of males at p o n d s ...... 53

12 Records of males observed on two or more dif­ ferent days at ponds 36 and 3 7 ...... 54

13 Movements of females to p o n d s ...... 57

14 Movements of females to ponds 36 and 37 • • • • 58

15 Movements of females between areas away from ponds ...... 60

16 Records of females at p o n d s ...... 61

17 Records of females observed on two or more different days at ponds 36 and 3 7 ...... 83

18 Prey of a d u l t s ...... 72

19 Recoveries of marked individuals . 81 v LIST OF ILLUSTRATIONS

Figure Page

1 Delaware Reservoir Wildlife Area ...... 4

2 Map of field a r e a ...... 5

3 Map of field area in vicinity of ponds 33 to 37* 6

4 The marking system ...... 13

5 A marked female Er.ythemis simplicicollis .... 16

6 Seasonal distribution of emergence: 1959 .... 22

7 Seasonal distribution of emergence: I960 .... 23

8-17 Color patterns of females and maturation period males: dorsal view of abdomen ...... 28

18 Occurrence and duration of color stages in individuals marked the day of emergence . . 31

19 Movements of males in vertical circling .... 49

20 Lengths of nymphs in samples...... 85

vi INTRODUCTION

The Odonata, large aerial insects with conspicuous preda­ tory and reproductive activities, have attracted considerable at­ tention. The literature contains abundant taxonomic works, lists of Odonata fauna, and more or less random observations on various aspects of behavior in many species. However, the biology and particularly the behavior of only a few species has been studied under field conditions over an entire flight season.

Borror (1934) studied movements and color changes during the adult life of the damselfly Argia moesta. Jacobs (1955) in­ vestigated the reproductive behavior of Plathemis lydia and

Perithemis tenera. Corbet (1957), in field studies, worked out the life history of a European Aeschnid, Anax imperator. Kormondy

(1959) studied the ecology and life history of three species of

Tetragoneuria. The subject of this study, Erythemis simplicioollis, a very common Libellulid, has been reared under laboratory con­ ditions from egg to adult (Bick, 1941). Other than this, and apart from brief notes on its behavior and feeding in general papers, the species has not been studied in detail.

The concept of territorialism has received considerable attention in vertebrate animals, and in recent years several workers have investigated and discussed this behavior in Odonata. St. Quentin (1934) noted that individuals of several European

species of Aeschna and Somatochlora flew about in a particular

restricted area from which other dragonflies of approximately the

same size were expelled. He termed these areas "Jagdrevieren" or

hunting grounds and assumed that they were primarily sites of

predatory activity, both over land (Landrevieren) and over water

(Wasserrevieren). Moore (1952) found that males of several species

of Anisoptera would sometimes couple with other males which were

suspended from strings, and he therefore interpreted the spacing

of dragonflies over their breeding grounds as the result of clashes

between males which were sexual rather than aggressive. Jacobs

.(1955) regarded localization of individual male dragonflies to

one part of a pond during adult life and the expulsion of other

males of the same species from the area as evidence of territorial

behavior whether the motivation was sexual or aggressive. Kor-

mondy (1959) concluded that occupation of a specific area by male

Tetragoneuria constituted a passive defense of territory.

In this study, large numbers of E. simplioicollis were

identified individually by marks on the wings so that any tendency

for individuals to become localized and to show territorial be­

havior could be recognized. Marked individuals would also indicate

movejments.about the area studied, color changes during adult life,

duration of adult life, and repetition of reproductive activities. METHODS OP STUDY

The Field Area

All of the field work in this study was done during the summers of 1959 and I960, in part of the Delaware Reservoir Wild­ life Area, a public hunting and fishing preserve operated by the

Ohio Department of Natural Resources (Figure l). This state-owned property of about 4»000 acres is located around the Delaware

Reservoir north of Delaware, Ohio. Forty-five artificial ponds, formed by earth dams, are scattered throughout the area. This study was conducted in a part of the wildlife area located in

Marion County, north of state route 229> about a mile east of

Norton, Ohio. The work was concentrated around five ponds, with occasional visits to five additional ponds on the periphery of the area. These ponds will be designated in this paper by the numbers assigned by the management of the wildlife area.

Figure 2 is a map showing the relative location of all the ponds included in this study. The area in the vicinity of ponds 33 to 37» where I did most of the work, is shown in greater detail in Figure 3» The fields near ponds 36 and 37> where dragon­ flies were collected and marked, were divided into fifteen areas, which were designated by numbers as shown in Figure 3.

Pond 36, the largest pond, was about 200 yards long and covered approximately 1.8 acres. It lay in an elongated depression 3 OHIO DEPARTMENT OF NATURAL RESOURCES FIGURE I. DIVISION OF WILOLIFE DELAWARE RESERVOIR WILDLIFE AREA PUBLIC HUNTING ANO FISHING +

DFFtCr UNLIT M i l

P , r * LEGEND U.S. £ State Highway! County & Area Roada Open Land (See Note BelowJ Hood Land (See Note Below) Boat Rental Parking, Toilet, Mater State Park Land - No Hunting prior to Oct. IS. Levee Ponds (See Note Below) Wildlife Pen Hunter Checking Station A free permit is required to hunt on the open and woodland after Noveaber 14. Some ponds are posted and closed to fishing each year for experimental purposes. Division offices will pro­ vide a list of open ponds and their species of fish. Ask for Publication N-343. JT FIGURE 2 MAP OF FIELD AREA

EDGE OF WOODS STREAM ROAD '37 FENCE CATTAILS POND DAM

SCALE

0.2 36

33

32

31(3

2 9 6 FIGURE 3 MAP OF FIELD ■> AREA IN VICINITY OF PONDS 33 TO 37

A. 12 EDGE OF WOODS 37 BOUNDARY OF COLLECTING AREAS STREAM CATTAILS POND DAM A. 8 A.7 COLLECTING AREA

SCALE t ■ ■ ■ t ioo » o FT. FT. 7

south of a strip of woods which separated it from pond 37* The

other three ponds were located about 180 yards south of pond 36.

Pond 33» the smallest pond, was almost circular, about 90 feet in

diameter, and was conneoted to pond 35 hy a marshy area.

Ponds 36 and 37 were about 10 to 15 feet deep next to the

dam; pond 35 was about 6 to 8 feet deep. Ponds 34 and 33 were

quite shallow, no more than 2 or 3 feet deep in most parts. All

the ponds were shallow around the edges and at the end away from

the dam.

Patches of Typha, Soirpus, and Sagittaria grew at the

edges and in the shallow areas of the ponds. All the ponds except

37 contained a thick growth of Chara and were partially covered by mats of filamentous green algae. The extent of these algal masses

varied. At times about three-fourths of the surface of pond 36 was covered by a floating mass of algae several inches thick.

Pond 37 was comparatively free of vegetation except around

the edges. In 1959 there was a narrow mat of algae and duckweed

along the shores, but in i960 this pond had almost no algal growth

and little vegetation of other kinds.

Pond 32 (Figure 2) had a large dragonfly population and

was visited more frequently than the other outlying ponds. It was

shallow, with an extensive cattail marsh on the east side. The

entire water surface was usually covered by duckweed. Periodic

checks for dragonflies were made at the other peripheral ponds.

Pond 31 was very small and muddy with little vegetation and few

dragonflies. Pond 29 was shallow and marshy, and pond 40 was fairly deep and clean, with little algal growth hut with large patches of Sagittaria. A large cattail marsh surrounded pond 38.

The fields between the ponds were abandoned pastures con­ taining extensive patches of blackberry and greenbrier. Teasel « - and goldenrod were the predominant herbaceous plants in these areas.

The wooded sections were brushy second growth.

The Odonata fauna of the area, for the most part, consisted of typical pond-breeding species, several of them very abundant.

The 36 species observed during the summers of 1959 and I960 are listed below. The most abundant Libellulids were Erythemis

Bimplioicollis, Pachydiplax longipennis, Libellula luotuosa, and

Plathemis lydia.

The Odonata observed or collected at ponds 32 to 38 in the

Delaware Reservoir Wildlife Area during 1959 and i960 were as follows!

Gomphus graslinellus Walsh Anax .junius (Drury) Anax longipes Hagen Epiaesohna heros (Fabricius(Fabriciu Epicordulia princeps (Hagen

Celithemis elisa (Hagen) Celithemis eponina (Drury) Libellula luotuosa (Burmeister) Libellula pulohella Drury Libellula semifasoiata Burmeister Plathemis lydia (Drury) Leucorrhinia intacta (Hagen) Sympetrum rubicundulum (Say) Sympetrum vicinum (Hagen) Erythemis aimplioioollis (Say) Pachydiplax longipennis (Burmeister) Tramea Carolina (Linnaeus) Tramea laoerata Hagen Pantala hymenea (Say) 9

Agrion maculatum Beauvois Lestes dis.junotus australis Walker Lestes dryas Kirby Lestes rectangularis Say Lestes unguiculatus Hagen Argia apioalis (Say) Argia violacea (Hagen) Enallagma antennatum (Say) Enallagma aspersum (Hagen) Bnallagma basidens Calvert Enallagma civile (Hagen) Bnallagma geminatum Kellicott Enallagma signatum (Hagen) Isohnura posita (Hagen) Isohnura prognatha Hagen Isohnura verticalis (Say)

The Species Studied

Erythemis simplioicollis is the only northern representative of a widespread genus of neotropical Libellulid dragonflies. This species has a very wide distribution and is usually quite abundant.

Needham and Westfall (1955) list it as occurring in 38 states, in

Ontario and Quebec, in Cuba, Haiti, and Jamaica. It is a pond- breeding species. The flight season is long in the north and adults occur the year round in the southern parts of the range.

Adults of E. simplioicollis are medium sized, clear-winged dragonflies. Total length ranges from 38 to 43 mm., length of front wing from 32 to 34 mm., and length of hind wing from 30 to

33 mm. (Byers, 1930; Needham and Westfall, 1955)* Females and young males are bright yellow-green marked with black and brown as follows (Figures 8-17): face pale green, vertex and occiput darker; thorax green with black edging on carinae, black or brown spots above coxae; legs black; abdominal segments 1-3 green, all carinae black; segments 4-6 with mid-dorsal black or brown spots, 10 varying in size and shape; segment 7 mostly dark with a rounded dorsal yellow-green spot; segments 8-9 mostly brown or black, segment 10 pale; superior appendages yellow; inferior appendage black. Older males become completely dull blue in color. The legs bear long black spines on the tibiae, shorter spines on the hind and middle femora, and three very long spines at the distal end of the hind femora. Mg is smoothly curved, the midrib of the anal loop is angulate; there are two cross veins under the stigma, a single bridge cross vein, three paranal cells before the anal loop in the hind wing, and six paranal cells before the subtri­ angle in the front wing. The stigma is brownish, with the front and rear sides about equal in length.

The nymph has a rather short, stocky body. Total length in the last instar is 15-17 mm* Dorsal hooks are absent. The nymph is easily separated from all other Libellulids occurring in

Ohio by the form of the inferior caudal appendages which are strongly decurved at the tip.

This very common insect has been the subject of only a few studies. Say (1839) described the species, placing it in the'genus

Libellula and basing his description on female specimens and on one young male. Needham (Needham and Betten, 1901) described the nymph. Williamson (1900) in his Odonata of Indiana, mentioned a few observations of behavior in this species, including one of the common interactions between males. Williamson (1923) and Kennedy

(1923) discussed the distribution and interspecific relationships 11 of the genus Erythemis. Bick (l94l) reared the insect from egg to adult and described morphological changes during the nymphal period.

Field Work

During the flight season of E. simplioicollis the field area was visited at least three or four days a week. In June and

July, when tenerals were most numerous and considerable time was devoted to marking, the area was worked five or six days a week.

The time spent in the field eaoh day varied but usually I was in the area six or seven hours unless interrupted by persistent rain.

Most dragonflies were captured and marked in the areas near ponds 36 and 37* These areas were covered in succession on each day in the field and as many unmarked E. simplioicollis as possible were captured and marked. Recaptures or observations of previously marked individuals were recorded at the same time.

Some individuals were captured and marked at ponds, usually in conjunction with observations of behavior when it was desirable to distinguish certain individuals at a pond. Females observed ovipositing were captured and marked whenever possible.

Ponds were checked for the presence of marked individuals by slowly circling the edges and examining the dragonflies flying over the water and along the shores. The outlying ponds were checked in this manner about once a week. Ponds 33* 34» and 35 were checked approximately every other day in the field. Ponds 36 and 37 were visited almost every day. When observations were being 12 made of behavior and reproductive activities several hours were usually spent at one pond. More time was spent in the areas away from ponds while tenerals were numerous. After mid-July most of the field work was at ponds.

Marking Adults

There have been several studies in which Odonata were marked so that recaptured individuals could be recognized. Borror

(1934) studied movements and color changes in the damselfly, Argia moesta, and marked individuals by dots of india ink on the wings.

St. Quentin (1934) attempted to determine how long dragonflies remained in one area by marking individuals with small pieces of white cloth and by cutting pieces from the wings. Moore (1952), in a study of territorial behavior in several species of Anisop- tera, marked captured individuals with oil paints on the wings.

He also squirted cellulose paints from a hypodermic syringe onto flying or resting dragonflies and recorded the position of paint on the body and wings of each individual. Jacobs (1955), in a study of territorialism and sexual selection, marked individuals of Plathemis lydia and Perithemis tenera with enamel paint placed on the thorax, wings, and abdomen. Corbet (1952), in a population analysis of the damselfly Pyrrhosoma nymphula« used cellulose paints applied to the thorax, abdomen, bases of the legs, and bases of the wings, to indicate the date of marking.

In this study I marked adults with dots of paint placed on the wings. Most individuals were captured by dropping an ordinary 13 aerial net over the insect as it perched or hovered in low vege­ tation or rested on the ground. Dragonflies caught in this manner were rarely injured. A few were netted on the wing hut this method was avoided because the insect was often stunned or broken.

Several brands of model airplane dope were used for mark­ ing. These inexpensive paints are waterproof, quiok drying, dur­ able, and quite satisfactory for marking purposes. The paints were carried in the field in two-dram vials. A captured dragonfly was held by its folded front wings and the costal edges of its hind wings while marks were placed on the underside of the wings with ’ a toothpick set in the cork stopper of the paint vial.

Dots of paint were placed on the wing in three locations, the number of dots in each area indicating a digit of an identi­ fying number. Marks at the tip of the wing, behind the stigma, indicated the units digit; those in the middle of the wing, at the level of the nodus, indicated the tens digit; marks at the base of the wing, behind the triangle, indicated the hundreds digit.

Usually no more than three dots were placed in the tens and units position and no more than one at the base of the wing. The ab­ sence of marks in any of these positions was recorded in the iden­ tifying number as a zero. Only the hind wings were marked on most individuals. I marked a few dragonflies on one or both front wings because the hind wings were injured or crumpled. During this study I used three colors of paint: red, yellow, and orange.

In recording the marks each three digit number was prefixed with letters indicating the wing marked and suffixed with a letter 14 indicating the color used. Figure 4 illustrates the marking system and Figure 5 shows a marked female.

In this manner many identifying marks could he devised, numbers were used in regular sequence throughout the study. As each insect was marked its number and other pertinent data were recorded in a notebook. I could spot marked dragonflies in flight, and could often read the marks when the insect was at rest without recapturing it. Binoculars were used considerably in spotting and reading marks. Dragonflies infested with mites received an ad­ ditional mark on a front wing, usually a single dot of a color different than that used on the hind wings, indicating that the individual should be recaptured for examination of the mite in­ festation. Records of recoveries of individuals were entered in a field notebook and were later transferred to 3 X 5 cards, a separate card for each recovery.

Individuals were usually released near the center of the area in which they were marked. Newly emerged tenerals were usually caught as they fluttered out of vegetation at pond edges.

The adjacent area into which the teneral flew upon release was recorded as the area of marking.

Table 1 summarizes the number of individuals marked, the number recovered, and the total number of recoveries. Table 2 shows single and multiple recoveries of individuals. 15

LH 002

RH 021

Figure 4* The Marking System 16

Figure 5. A Marked Female Erythemis simplioicollis 17

Table 1. Marking and Recovery Summary

1959 I960 Total

Number 700 Marked 635 1335

Number 270 Males Recovered 243 513 Per cent 38.27 38.57 38.43

Total 378 Recoveries 419 797

Number 720 Marked 1115 1835 Number 228 619 Females Recovered 391 Per cent 31.67 35.07 33.73

Total 692 Recoveries 349 1041 Number 1815 3170 Marked 1355 Number 471 661 1132 Total Recovered Per cent 34.76 36.42 35.71

Total 727 1111 1838 Recoveries 18

Table 2. Single and Multiple Recoveries

Number of Individuals Times I960 Total Recovered 1959 Fe­ Fe­ Fe­ Males males Total Males males Total Males males Total

1 159 151 310 179 232 411 338 383 721

2 51 44 95 52 93 145 103 137 240

3 21 25 46 24 33 57 45 58 103

4 8 5 13 11 9 20 19 14 33

5 3 3 6 4 12 16 7 15 22

6 8 8 8 8

7 1 1 2 2 1 2 3

8 1 1 1 1

9 1 1 1 1

Total 243 228 471 270 391 661 513 619 1132 THE ADULT

Emergence

The nymph of E. simplioioollis leaves the water before its final molt hut transformation apparently occurs close to the pond.

Exuviae of nymphs were usually found on plant stems within six inches of the water. They were on both plants growing in the pond and on the shore. Occasionally I found exuviae floating in the water or resting at the water edge. Two were found on floating algae.

Nymphs and newly emerged tenerals were very inoonspicuous and could be located only by carefully searching through vege­ tation along the shores of ponds. I was able to find only three nymphs actually in the process of transformation. All three were clinging to vegetation. Two were on grass stems, an inch or two from the ground, and one was on a Sagittaria stalk, in the pond, about 4 inches above the water. One was just beginning emergence but the others were partially out of the nymphal exoskeleton when first discovered. The time elapsed during the various stages of emergence is summarized in Table 3. All times are eastern stand­ ard A.M.

The wings of all three individuals had begun to expand before the abdomen was completely free and the process was com­ pleted fairly rapidly. However, none of them was capable of 19 20

Table 3. Time Elapsed During Stages of Emergence

Wings Able Thorax Head Wings Abdomen Expanded to Date Split Free Free Free (approximate) Fly

6/6/60 6:22 6:34 6:37 6:55 7:13 8:01 6/10/60 6:51 6:58 7:15 7:42 7/11/60 5:37 5:41 6:03 6:27 6:45 (fell in pond) 7:25 flight immediately. When disturbed they fell, with weak flut­ tering of wings, into the vegetation. The third individual flew a few feet about 18 minutes after the wings seemed to be fully esqpanded but it fell into the water. The last column in Table 3 gives the time when the individual was first prodded into sustained flight.

Very weak tenerals, which would not fly until actually dislodged from their resting place, were fairly abundant between

5:30 and 7:00 A.M. on five days in June and July, I960, when the shore of pond 36 was examined at this time of day. Newly emerged dragonflies could be flushed from pond edges until mid-afternoon although they were more numerous during the morning hours. Pew were found away from the ponds until afternoon. Several careful searches for emerging nymphs were made during mid-morning hours but none were found. Twice I examined pond edges between 8:00 and 10:30 P.M. and again no nymphs were discovered. Apparently emergence occurs for the most part in the early morning prior to 21

5s30-6sOO A.M., "but unless disturbed the newly emerged dragonflies tend to remain at the pond edge until mid-day.

Tenerals flushed at the pond edges generally rose at least four or five feet in the air and flew in a fairly straight line away from the pond. I saw only one individual fly over a pond; it failed to cross and dropped in the water about 30 feet from the shore. After this first flight most of the dragonflies settled into vegetation again and remained motionless, holding their wings folded together. They were very difficult to see in this situation since their protective coloration was excellent camouflage, at least to the human eye. Many of them, however, took flight again when approached closely. Sometimes a teneral pursued away from the pond would rise high in the air and fly into trees at the edge of the woods. Individuals often traveled 50 feet or more with these direct, sustained flights.

Seasonal Distribution of Emergence

The first newly emerged teneral was found May 18, 1959> and May 26, i960. The last of the season was seen August 12, 1959 > and September 1, i960. Between these extremes at least a few newly emerged adults could be found almost every day. However, there were periods when emergence was obviously greater and teneral dragonflies were most abundant in the fields around the ponds.

Figures 6 and 7 show the mean number of teneral males, i.e., green-black males, captured and observed in areas 1 to 10, on days these areas were worked, during weekly periods from the end of May 22-

FIGURE 6 . SEASONAL DISTRIBUTION OF EMERGENCE I S 5 9

40

30 MEAN NUMBER TENERAL 85 MALES CAPTURED DAILY IN AREAS I TO 10

WEEK 28 4 II 18 25 2 9 16 23 30 6 13 20 27 3 ENOING IMAY JUNE JULY AUGUST SEPT. 23

FIGURE 7. SEASONAL DISTRIBUTION OF EMERGENCE I 9 6 0

40r

MEAN NUMBER TENERAL MALES CAPTURED 20 DAILY IN AREAS I TO 10

WEEK 26 4 II 18 25 2 9 16 23 30 6 13 20 27 3 ENDING MAY JUNE JULY AUGUST SEPT. 24 through August. Several days when collecting was interrupted hy had weather were omitted in calculating the weekly means. Green- hlack males are almost always less than a week past emergence and the relative abundance of these young dragonflies over the season should he an indication of the seasonal pattern of emergence.

In hoth years there were three peaks of emergence in June and July, after which the number emerging dropped off sharply.

After mid-August only a few teneral males could he found in the entire area although emergence continued until ahout the first of

September.

The first peak period came ahout a week earlier in 1959 than in I960 and the maximum in 1959 was reached around the first of July. This was followed hy a sharp deoline in the second week in July and hy a moderate rise the week ending July 23* In i960 there was also a peak around July first hut the mid-July period showed a lesser decline than in the previous year and the greatest peak of teneral males came around July 23. In the week following the last peak teneral males almost completely disappeared from the area.

Data from samples of nymphs gave no indication of more than one generation per year (these data will he presented and discussed in the section on the nymph). These peaks of emergence do not represent the appearance of successive broods; all the adults emerging in one flight season are presumably the offspring of the adults of the previous summer. 25

Maturation Period

The maturation period is the time after emergence during which young dragonflies remain away from ponds. In the area studied young E. simplicicollis were particularly numerous during this period in areas 1 to 10 along the edges of woods, in clearings and around blaekberry-brier patches. The end of the maturation period and the beginning of the reproductive period is marked by initiation of breeding activity at ponds and by changes in oolor- ation which are especially striking in males.

Adults have a characteristic appearance on the day of emergence and may be reoognized as new tenerals by their irri- descent and slightly clouded wings. After the first day the wings are clear and dry, and although the insect remains somewhat soft- bodied throughout the maturation period its appearance does not indicate the exact passage of time since emergence.

Coloration

Both sexes are bright yellow-green at emergence, with a pattern of black and brown on the abdomen. The extent and inten­

sity of these markings varied considerably. I established four

classes of color pattern based on the extent of black on the dorsum

of the fourth to ninth abdominal segments. These categories were

designated, from lightest to darkest, by the letters a_, b, c^, and

d. Whenever possible the olass of coloration was recorded for

each green-black individual marked or recovered. Figures 8 through 26

15 show the four categories of color pattern in both males and females.

New tenerals exhibited all four patterns but the majority of the males fell into the two darker classes, while the majority of the females were classified in the two lighter categories.

Table 4 summarizes the coloration of newly emerged individuals.

Table 4• Color Patterns of Individuals Marked on Day of Emergence

Number of Individuals

Color Pattern Males — Females

a 26 99 b 34 80 0 58 60 d 101 38

In many individual cases the extent and intensity of the dark color pattern increased during the maturation period. I have

90 records of males and 312 records of females in whioh the dark pattern increased one or more categories. Apparently almost all of the individuals classified as a or b at emergence eventually become £ or d.

The blue coloration of males first appears on the dorsum of the fourth, fifth, and sixth abdominal segments and soon ob­ scures the black and green pattern of the entire abdomen. The dorsum of the thorax also becomes pruinescent and blue. The three basal abdominal segments and the pleural regions of the thorax 27

Figures 8-17

Color Patterns of Females and Maturation Period Males:

Dorsal View of Abdomen

Figure

8 Male a_

9 Female a

10 Male b

11 Female b^

12 Male o

13 Female c_

14 Male d

15 Female d^

16 Male, early intermediate

17 Male, late intermediate ($] ^ H W e »(lE3gg3»g 14 18 29 remain green for some time, but eventually the entire body of the

insect is a uniform dull blue. On the abdomen the pale green mid- dbrsal spot on segment 7 remains visible longer than the rest of

the green-blaok pattern. In recording the ooloration of males I used the first appearance of blue on the abdomen and the disap­ pearance of the spot on the seventh segment as criteria marking respectively the beginning and end of the intermediate stage be­

tween green-blaok and blue. Figures 16 and 17 show abdomens of

males in early and late intermediate stage. All males found in

early intermediate coloration had either c or d green-blaok pattern.

During the two summers I obtained 197 records of males which were green-black when marked and which were recovered at

least once while still green-black. One of these remained in this

color stage 10 days after being marked} one was still green-black

after 8 days; all the other recaptures were 7 days or less after

the first observation. These data indicate that the green-black

coloration rarely persists in males longer than a week. Sixteen

individuals were observed two or three times in the intermediate

stage of coloration end in all instances the last observation was

no more than 2 days after the first. All of the 177 individuals

changing from green-black to blue between two successive obser­

vations were recaptured at least 3 days after the first record.

The change to blue seems to occur rather rapidly, probably within

3 days, which would account for the small number of repeated ob­

servations of males in intermediate coloration. 30

Ten males marked on the day of emergence were recovered In intermediate coloration 6 to 11 days later. No males were re­ covered with blue coloration sooner than 8 days after emergence and only two were recovered earlier than the tenth day. There seems to be individual variation of a few days in the age at which males undergo these color changes. Figure 18 A, which is based on

147 recoveries of 79 males marked on the day of emergence, diagrams the occurrence and duration of the color stages in the adult life of males.

Females do not undergo a general color change but the venter of the abdomen eventually becomes gray-blue and a slight bluish pruinescence somewhat obscures the color pattern on the dorsum of the abdomen. ' Older females are duller in general ap­ pearance and the green-black pattern is less sharply defined than in newly emerged individuals. The time of the appearanoe of this slight pruinescence in females roughly corresponds to the develop­ ment of wholly blue color in males. The earliest record of prui­ nescence in females was 8 days after emergence. Sixty-two of the females marked on the day of emergence were recorded as non- pruinose 1 to 16 days later. Other females, which were marked after the day of emergence, were listed as remaining non-pruinescent up to 18 days. The first occurrence of pruinescence could have been overlooked in many of these individuals because it often is not evident unless the insect is examined closely. The overlap in the ages of non-pruinose and pruinose females possibly is not as JDL

FIGURE 18. OCCURRENCE AND DURATION OF COLOR

STAGES IN INDIVIDUALS MARKED THE DAY OF EMERGENCE

A. MALES

BLUE

INTERMEDIATE

GREEN-BLACK 1 1 » » ■ ■ « ■ — ..... DAYS AFTER 5 10 15 20 25 30 35 40 45 50 55 60 EMERGENCE

B. FEMALES

PRUINOSE

NON-PRUINOSE

DAYS AFTER 5 10 15 2 0 25 30 35 40 45 50 55 60 EMERGENCE 32 great as the data available seem to indicate. Figure 18 B, which is based on 151 recoveries of 80 females marked the day of emerg­ ence, diagrams the occurrence of pruinescence in females*

Behavior and Movements

Tenerals of E. simplioicollis were usually found flying slowly about in patches of vegetation. They perched frequently on stems, low shrubs, or fallen branches, and unless disturbed rarely flew more than a few feet at a time or rose more than two or three feet from the ground. Individuals watched continuously for periods varying from 20 minutes to about two hours wandered about considerably but none covered an area greater than approxi­ mately 750 square feet and most remained within 200 square feet.

A number of individuals in the same area usually flew about in close proximity. There was no evidence of any interaction between indi­ viduals or of any tendency for individuals to become localized in a particular spot within the general area. An individual rarely perched on the same support twice, although a particular resting place might be used successively by several different dragonflies.

Occasionally an individual would dart at another passing E. simpli-

cioollis or at another species of dragonfly and then immediately

return to its perch. This movement appeared no different than the

response to any large insect flying past. They frequently flew in

the same manner at large Lepidoptera, at bumble bees, or at large

tabanids which they did not take as prey. 33

On clear days the dragonflies were usually found in open or partly sunny areas, rarely in full shade. However, activity of

individuals during the maturation period did not seem to be greatly reduced on overcast days. Even during cool, rainy weather many tenerals could be found flying about.

Conclusions about the movements and dispersal of E.

Bimplicicollis during the maturation period must be largely drawn

from recaptures of males since the appearance of an individual female does not clearly indicate the stage of its adult life. How­

ever, coloration of males gives a fairly accurate indication of age

and also appears to indicate reproductive maturity. No green-black

males were seen flying over ponds and although individuals of

intermediate coloration were found at breeding sites, only one, a

very late intermediate, was observed in copulation. All records

of green-blaok and intermediate males are considered to be in the

maturation period although there may be a slight overlap, by some

late intermediates, with the reproductive period. Reoords of inter­

mediates at ponds will be discussed in,the section on the repro­

ductive period.

The development of reproductive maturity and the end of

the maturation period in females is not readily evidenced by color

change. The pruinescence which apparently begins to develop at

this time is quite inconspicuous until about three weeks past emerg­

ence. Many females seen ovipositing appeared to be non-pruinose.

Breeding age females spend relatively little time at ponds and are

usually found flying about in the same area as young dragonflies 34

still in the maturation period. Females found away from the ponds and recorded as non-pruinose cannot with any certainty he plaoed in the maturation period. However, since no females were seen at ponds sooner than eight days past emergence, records of females marked as new tenerals and recaptured within a week can he used to represent the maturation period. Again there may he some over­ lap with the reproductive period.

Tahle 5 summarizes recoveries of 240 males and 61 females during their maturation periods. Recoveries of 49 males marked the day of emergence and included in the total in the first column

are also listed separately for comparison with the females.

These recaptures indicated relatively little dispersal.

All recoveries of insects still in the maturation period,-with the

exception of intermediate males at ponds, were in Areas 1 to 10, where all of them were marked. Fields and wood edges in the

vicinity of ponds on the edges of the area studied were checked

ahout once a week hut no marked individuals were found.

Most individuals tended to remain in a relatively limited

area and few of those recaptured crossed the strip of woods between

ponds 36 and 37* Eleven females, 18.03 per cent of those recovered,

were observed on both sides of the woods. Only 11.67 per cent of

the males, 28 individuals, crossed the woods. No males were ob­

served in more than three different areas and no females in more

than two. Of the 212 males remaining on one side of the woods, 198

(82.5 per c®nt of the total 240) remained in the same area or moved

into a directly adjacent area; 46 of the 50 females remaining on 35

Table 5* Repeated Observations of Individuals, in Areas 1 to 10, During the Maturation Period

Number and Percentage of Individualsa

Males Marked Females Marked Day of Day of Observation All Males Emergence Emergenoe

Observed in one 135 24 30 area only 56.25 48.98 49.18

Observed in two 99 24 31 different areas 41.25 48.98 50.82

Observed in three 6 1 different areas 2.5 2.04

Observed on one 212 42 50 side of woods 88.33 85.71 81.97

Observed on both 28 7 11 sides of woods 11.67 14.29 18.03

Total 240 49 61

^ h e upper figure in each entry is the number of indi­ viduals and the lower is the percentage of the total. one side (75*41 per cent of the total 6l) stayed in the same or in directly adjacent areas. Thus over 80 per cent of the males and about 75 P®r cent of the females showed very little movement during their maturation period, being observed two to five times in the same general locality.

The flight behavior of newly emerged individuals is quite different from that observed during the rest of the maturation period. Much of the local dispersal probably occurs during the first day of adult life when the dragonflies tend to make long,

sustained flights. Later, although the individuals spend more time 36 flying, it wanders erratically, back and forth in the same locality, moving only a few feet at a time. The percentage of individuals crossing the woods and of individuals observed in more than one area is higher for males marked the day of emergence than for all males. This probably reflects wider dispersal of these insects during the first part of the maturation period. The other males were marked one or more days after emergence and were already ex­ hibiting the typical pattern of short localized flights. The per­ centages of females, all of which were marked the day of emergence, correspond almost exactly with those of males marked the day of emergence and observed in one area and in more than one area.

However, a somewhat larger percentage of females crossed the strip of woods and the percentage found in the same or in adjacent areas is smaller.

Reproductive Period of Males

After the maturation period adults appear at the ponds and reproductive activity begins. Mature blue males were found at ponds continuously during favorable weather and individuals often remained for periods of several hours. Females were encountered at ponds less frequently because they remained only a few minutes while mating and ovipositing.

Intermediate Males at Ponds

Most of the males observed at ponds had their blue color­ ation well developed but a few were still in the intermediate stage.

Table 6 lists all records of marked males at ponds and away from 37

Table 6. Total Records of Males (Number Marked Plus Total Recoveries)5

Location Color At Ponds Away from Ponds Total

1197 1197 Green-black 100.00 100.00 77.23 56.14

19 127 146 Intermediate 13.01 86.99 100.00 3.26 8.19 6.85

563 226 789 Blue 71.36 28.64 100.00 94.74 14.58 37.01

582 1550 2132 Total 27.30 72.70 100.00 100.00 100.00 100.00

^ p p e r of three figures in each entry is number of records, middle figure is per cent of total of that color, lower figure is per cent of total in that locality. ponds. The total of intermediates at ponds includes 13 indi­ viduals which were marked when green-black and recovered as inter­ mediates at ponds, 4 others which were intermediate when captured and marked at ponds and 2 recoveries of these individuals at ponds while still intermediate. This total of 19 records of marked intermediate males at ponds is 13*01 per cent of the 146 records of intermediate males and 3*26 per cent of the records of males at ponds. Observations at ponds make up 71*36 per cent of the 789 records of blue males. Fourteen of the intermediate males at ponds were late stage, with the abdomen almost completely blue.

Eight of the intermediate individuals found at ponds were kept under observation until they flew away from the water. These 38 observations are summarized in Table 7* These intermediate males ■ ¥ remained at the pond for relatively brief periods, ranging from

minutes to about 21 minutes, after they were first discovered.

However, six of them left after the approach of a blue male and five of these participated in typical interactions as described under Behavior at Ponds, with the blue male. None of these eight individuals was found at the pond later the same day but one re­ turned the next day and one was observed at the same pond 21 days later. Both were blue at the time of this second observation.

One unmarked late stage intermediate was seen in oopu- lation and its behavior was not noticeably different from that of blue males. This observation was on June 2, I960, a cool, partly overcast day when very few E. simplicicollis males were at the ponds. No other males approached during this mating and the fe­ male completed oviposition undisturbed. The intermediate male left the pond shortly after the female.

Movements to Ponds

Recoveries of males included 237 observations (233 indi­ viduals) at ponds that were preceded by a record away from ponds.

The first two columns of Table 8 list movements to ponds by 186 males which were not blue at the time of the last record in areas

1 to 15 prior to the initial observation at one of the ponds. In the interval between the two observations 10 of these individuals changed from green-black to intermediate, three remained inter­ mediate, 21 changed from intermediate to blue, and 152 changed from 39

Table 7* Observations of Some Intermediate Males at Ponds

Time Individual Remained at Pond Bate Pond (minut essseconds) Notes

early intermediate, flew into 8/7/60 36 2:31 area 1 at approach of blue male.

interaotiona with blue male, 6/6/60 37 4:11 flew into area 8, in area 10 later same day

6/11/60 36 7*02 interaction8, with blue male

7/18/60 36 8:42 interaction8, with blue male, returned to pond 36, 7/19/60

8/6/60 36 9*57 flew into area 2

7/16/60 36 11:41 flew into area 2

7/19/60 36 12:23 interaction8, with blue male, in area 3 later same day

7/12/60 36 21:04 interaction8, with blue male, returned to pond 36, 8 /2/ 6O

aAs described under Behavior at Ponds. green-blaok to blue. This group presumably is composed principally

of males moving to ponds in the early part of the reproductive period. Fifty-one of the movements to ponds were by blue males.

These are summarized in the last two columns of Table 8. This

group of older males includes four of the individuals listed in

the first two columns which moved to a pond a second time after an

intervening record away from ponds. Table 9 analyzes movements to

ponds 36 and 37. 40

Table 8* Movements of Males to Ponds

Number of Movements

- Males Whioh Were Not Blue Both Observationsa Blue Males

To Prom Prom Prom Prom Pond Areas 1 to 6, Areas Areas 1 to 6, Areas Number 14, 15 7 to 10 14, 15 7 to 10

37 9 8 2 3 36 117 27 34 9 35 12 4 1 34 3 1 33 3 1 32 1 1 38 1

Total 145 41 38 13

individuals remaining intermediate, changing from green- black to intermediate or to blue, or changing from intermediate to blue; number of each is given in text.

More records were obtained of males moving to ponds from areas 1 to 6, 14 and 15 than from areas 7 to 10. Dragonflies were usually less abundant in areas 7 to 10 and fewer were marked in these areas than on the other side of the woods.

In movements to ponds 36 and 37 the percentage crossing the woods was much greater in one direction than in the other.

Prom areas 7 to 10 over 76 per cent of the movements were to pond

36. Only 6.79 per cent of the movements from the areas on the south side of the woods were to pond 37• In each case the percentage of blue males moving aoross the woods was slightly lower than that of the group containing younger individuals. 41

Table 9* Movements of Males to Ponds 36 and 37

Color When Observed Green-black Away from of Pond Intermediate Blue Total

Number 36 117 34 151 Moving Movement s to from Pond 37 9a 2a lla Areas 1 to 6, Per Cent Crossing Woods 7.14 5.56 6.79 14, 15 Total 126 36 162

Number 36 27a 9a 36a Moving Movement s to from Pond 37 8 3 11 Areas 7 to 10 Per Cent Crossing Woods 77.14 75.00 76.60

Total 35 12 47

®Moving across woods.

During the last half of the summer of 1959 and most of the

summer of i960 there was very little reproductive activity at pond

37. Vegetation was very sparse and oviposition sites were not

present. Lack of attraction to breeding sites at pond 37 probably

affected the percentage of movements across the woods between

ponds 36 and 37•

The movements of males from areas 1 to 6, 14 and 15

indicates that B. simplicicollis males tend to start reproductive

activity at a nearby pond when it contains abundant breeding sites.

However, the movements from areas 7 "to 10 indicate that many males

move to a more distant pond when the closest pond lacks breeding 42

sites. The number which ordinarily would have crossed to pond 36 from areas 7 to 10 probably was augmented by males which would have been attracted to and localized at pond 37 if it had contained more breeding sites.

About one-fifth were of the 187 movements to pond 36, from areas 7 to 10. Half of the 22 movements to pond 37 were from across the woods. If pond 37 had been a better breeding area the pro­ portion of males there from areas 7 to 10 probably would have been

greater and the proportion arriving at pond 36 from areas 7 to 10 would have been smaller.

Dragonflies were fairly abundant at ponds 33» 34 and 35

but relatively few of the E. simplicioollis marked in areas 1 to

15 were recovered there. Most of the males seen at these ponds

were unmarked. They probably emerged from these three ponds and

stayed in the surrounding areas during their maturation periods.

More males from areas 1 to 6, 14 and 15 moved to ponds 33» 34 and

35 than to pond 37 (Table 8) indicating that the wooded strip is

a greater barrier to dispersal than the open bushy fields south

of pond 36.

Two marked males were found at pond 32. One, in 1959» was

marked 17 days earlier in area 95 the other, in I960, was marked 22

days earlier in area 4. Both were green-black when marked and

fully blue when found at pond 32. One male, in I960, reached pond

38 from area 10 where it was marked when green-blaok and recovered

two daya later as an intermediate. The recovery at pond 38 was 27 43 days after this last observation in area 10. No marked individuals were found at any of the other outlying ponds.

Movements from Ponds to Areas Away from Ponds

Blue males found away from ponds were usually flying about in low vegetation in a manner similar to that of females or matu­ ration period males. Their movements tended to be somewhat quicker and if pursued or disturbed they often rose high in the air and left the area completely. No blue males were recorded more than twice in a given area away from the ponds.

Only 13 blue males were found in areas away from ponds after an observation at a pond on a previous day and it is difficult to draw conclusions from this small number. Six of these moved from pond 36 to adjacent areas and three from pond 37 to adjacent areas.

Four crossed the woods from pond 36 to areas 7 to 10. One indi­ vidual moving from pond 37 to area 8 was later seen twice at pond

36 and one moving from pond 36 to area 7 was back at pond 36 two days later. In addition to these records on different days, 16 blue males were observed in areas near pond 36 after a previous record at the pond on the same day.

Movements between Areas away from Ponds

Table 10 lists 385 movements of males between two succes­

sive records in areas away from ponds. The same individual is

represented several times in these summaries if it was recovered

three or four times in succession away from ponds. Bach successive

pair of observations is counted as one movement. In this usage 44

Table 10. Movements of Males Between Areas Away from Ponds8,

From Areas From Areas 1 - 6 to 7 - 10 to Color of Areas Areas Areas Areas Males 1 - 6 7 -10 1 - 6 7 -10 Total

Blue on one b b or both 76 9 8 23 116 observations 88.16 11.84 25.81 74.19

Green-black or b b intermediate 172 21 7 69 269 both obser­ 89.12 10.88 9.21 90.79 vations

b b 248 30 15 92 385 Total 89.21 10.79 14.11 85.89

®The upper figure in eaoh entry is the number of movements and the lower is the percentage of the total from that area.

^Movements across woods.

•'movement" refers to staying within one area during the interval between recoveries as well as travelling to a different area. Most

of the individuals staying on one side of the woods either remained

in one area or moved to a directly adjacent area. The first row

of the table includes 116 movements in which the individual was

blue both observations or in which it changed to blue from green-

black or intermediate between the two records. The second row

lists for comparison 269 movements by maturation period individuals

which were green-black or intermediate both observations.

The percentage of movements across the woods is highest

in the older group of males, those blue one or both observations. 45

However, it is not much higher than the overall percentage. Only

in this group is there much difference in the movements across the woods in opposite directions. The percentage crossing to areas 1

to 6 from areas 7 to 10 is over twice that moving in the other

direction. Again this is probably due to lack of attraction to breeding site at pond 37» failure of males to localize at that pond and subsequent movements across the woods with the obser­

vations in field areas probably coming between appearances at

the ponds.

Behavior at Ponds

Adult Libellulid dragonflies presumably spend the night in

fields or woods near ponds. Needham and Westfall (1955) in refer­

ence to E. simplicicollis state "At night it hangs up among foliage

of pondside or roadside weeds." Although searches were made for

dragonflies at night on two occasions none were located in the low

vegetation near the ponds. Males began to arrive at ponds, flying

in from adjacent fields, within 2 to 3 hours after sun rise, al­

though the number present at a given pond remained relatively

small until mid-morning.

Males at ponds, when undisturbed by other individuals,

repeatedly flew over a rather definite course covering a limited

area. The site of these flights was usually above a portion of a

pond containing floating algae, duckweed, or Sagittaria leaves.

Males were not observed flying in this manner over open water.

The size of the area covered was usually less than 150 square feet 46

and the flight pattern of the individual tended to conform to the distribution of floating vegetation. At ponds with a narrow hand

of algae along the shore males flew back and forth over a section

a few feet wide and up to 10 or 15 yards long. Where there were broad expanses of floating vegetation the area covered was usually

shorter and broader and the pattern of flight was elliptical or

almost circular. Most individuals flew only a few inches above the pond surface.

Males flying over the pond occasionally dipped the tip of

the abdomen in the water in a manner closely resembling the o p ­ position movements of females. This action always occurred over

patches of floating vegetation, sites where most opposition oc­

curred.

Flight over a pond was not continuous; most indiPduals

rested every few minutes, perching on stalks or plants protruding

from the water, on plants at the pond edge, or on objects floating

in the pond. Also, males frequently rested flat on an algae mat

or on bare ground along the pond shore. Individuals tended to

rest each time on one or two particular perches or on approximately

the same place on an algae mass.

When flat pieces of wood were floated in ponds these were

almost invariably utilized as resting sites by B. simplicioollis

males even when numerous protruding sticks and plants were avail­

able as perches. Also, males often alighted on the algae in areas

where there were many conspicuous perches. In this species there

seems to be a definite tendency to rest on a flat low surface. 47

Ten different males, each flying a straight, fairly long, back and forth course along a pond shore, were timed with a stop watch as they flew over a measured distance. The approximate speed of these flights ranged from 2*8 to 3*4 yards per second, with an average of 3.1 yards per second (about 6.4 miles per hour).

Usually a number of males were present in the same part

of a pond, each flying over its separate, more or less defined area. However, there were frequent encounters by males established

at the pond with eaoh other, and with newly arrived individuals.

When one male entered the flight area of another the two usually

performed a typical series of interactions which continued until

one of the two left the pond completely or moved to another area.

Upon first encountering each other two E. simplicicollis

males usually began a back and forth flight, moving almost paral­

lel, one slightly in advance of the other. After flying about 10

to 20 feet in one direction the pair would turn and reverse their

course. If one individual had been flying in front of the other

it now usually flew behind. The speed of these flights was ob­

viously greater than that of a single male cruising over the pond.

Timing this movement was difficult because of the increased speed

and the shorter and varying course followed. Seven such inter­

actions were timed in which the dragonflies flew back and forth

several times over approximately the same path and the total

distance covered could be estimated. The determined speeds ranged

from 6.8 to 11.2 yards per second, with an average of 8.4 yards per

second (about 17.2 miles per hour). 48

If both males remained after several of these parallel flights a second type of interaction, which I have termed vertical circling, usually occurred. This maneuver, however, was not always directly preoeded by parallel flights} it was sometimes performed immediately after the first encounter of two individuals.

In vertical circling the two males first hover almost motionless, both facing the same direction, one in front of the other, both at the same height above the pond surface. Then as the male in front moves upward, backward and downward, the one - behind moves downward, forward and upward reversing the original position. This process is repeated several times, with some for­ ward movement, as the two individuals describe a circular path in a vertical plane (Figure 19)• The number of position exchanges or half circle movements varied from one to nine. The movements were sometimes performed in rapid succession but frequently the two individuals paused and hovered again after three or four half circles and then resumed circling or went into parallel flight.

The two types of interaction, parallel flight and vertical cir­ cling, were often alternated several times.

The vertical circling interaction of E. sinrplioioollis was described by Williamson (1900) as follows:

On several ocoasions and at different lo­ calities males have been seen going through maneuverings which are hinted at frequently by some of the Libellulas, but which seem to have been perfected only in this species. Two males are necessary for the performance. They flutter motionless, one a few inches in front of the other, when suddenly the rear one will rise and FIGURE 19. MOVEMENTS OF MALES IN VERTICAL CIRCLING

POMP SURFACE

3 POMP aUWPACP pass over the other, which at the same time moves in a circle downwards, backwards and then upwards, so that the former position of the two is just reversed. These motions kept up with rapidity and regularity give the observer the impression of two interseoting oiroles which roll along the surfaoe of the water.

According to this report the males moved in a different manner than that previously described. The rear individual passed over instead of under the one in front. In every observation I had of this behavior the rear male moved beneath the other indi­ vidual. I have watched this movement only in Central Ohio popu­ lations of E. simplicicollis and perhaps in other populations the movement is forward and over instead of forward and under.

Interactions between males usually ended with one of the two individuals withdrawing from the site. The retiring male did not always leave the pond. It frequently moved only a short distance and settled into a flight pattern over an unoccupied site. One hundred ninety-two observations were made of inter­ actions in which at least one of the pair was marked and the two individuals could be distinguished throughout the encounter. In

42.17 per cent of the interactions between a male established over a site and one arriving from elsewhere the individual originally at the site was displaced by the newcomer. The new male quickly took up a definite flight course, usually similar to that followed by the previous occupant of the area.

Occasionally after a long series of interactions both males flew high in the air above the pond, usually moving out of sight.

This occurred nine times in encounters of one marked and one unmarked 51 male, and In four cases, within one or two minutes the marked male returned to the site of the previous interactions and began a flight pattern over the area. Whenever this high vertioal flight occurred a male flew in directly to the site within a few minutes.

Probably this was one of the two participants returning from the vertical flight but except in the case of the four marked indi­ viduals this can only be inferred. It could have been another male arriving from the surrounding field areas. Several times I observed that a third male flying nearby at the pond moved over a spot vaoated when two others went into vertiole flight. In each oase this third male was encountered within a few minutes by a male flying into the area, possibly one of the pair returning from the vertical flight.

On warm midsummer days E. simplioioollis males were present constantly over almost all pond sites with vegetation. Interactions and displacements occurred continually. When many males were flying over the mats of floating vegetation others would take up flight areas over sparsely vegetated areas where the Ohara growth was close to the surface. When males arrived at the ponds in the morning the well vegetated areas were always occupied first.

At pond 37 only a few males were present at a given time and these were usually flying over all available vegetated areas.

Displacements of males from this pond and movements away from the pond by newly arrived dragonflies after interactions with estab­ lished males probably increased the movements to other ponds from pond 37 and the surrounding areas. 52

The frequency and duration of interactions between two

males established over adjacent pond sections decreased after a

few encounters. Subsequent interactions between the two indi­ viduals usually consisted of only a few half circle movements,

after which each male retired to its respective flight area.

Interactions were totally intraspecific. Other species

of Libellulid dragonflies were present at the pond, frequently

flying in the same areas as the B. simplioicollis males, but for

the most part the different species completely ignored each other.

Occasionally a male of E. simplicioollis darted at a passing male

Pachydiplax longipennis, a similar sized, bluish species which

flies at about the same level above the pond. The P. longipennis

was never pursued any distance and the approached individual did

not show any response to the E. simplioicollis. However, P.

longipennis often were seen hovering, with the end of the abdomen

raised, in front of and facing an E. simplioicollis. This is the

position usually taken by P. longipennis males when meeting another

male of their species. Also P. longipennis sometimes flew behind

an E. simplioicollis for a short distance. These encounters never

lasted longer than a few seconds and there was never any response

by the E. simplioicollis. The two species often perched very close

together on the same support. Neither was ever seen resting in

close proximity to a male of its own species. Other Libellulids

at the ponds tended to fly and perch at different heights than E.

simplicioollis and there were rarely any encounters of any sort

between species. 53

Localization

A total of 397 individual "blue males were recorded (marked or recovered) at ponds as shown in Table 11. One hundred eighteen of these marked males were observed at ponds on two or more dif- s. ferent days. Only six of these individuals appeared at two dif­ ferent ponds. Three of these moved from pond 37 to pond 36, one from pond 36 to pond 33» one from pond 34 to pond 33> and one from pond 35 to pond 33 and back to 35* The time elapsed from the first to last pond record of the 112 individuals found at only one pond ranged from 1 to 42 days.

Table 11. Records of Males at Ponds

Total Individuals Individuals Records at Two Ponds

One day at pond 279 279 Two days at ponds 81 162 3 Three days at ponds 28 84 2 Pour days at ponds 8 32 1 Six days at ponds 1 6

Total 397 563 7

The appearance of most males at only one pond and the return of individuals to the same pond after as long as six weeks

indicates that E. simplicioollis males tend to become localized in

regard to a particular pond. However, on successive returns indi­

viduals were frequently found over different parts of the pond.

Pond 36 was divided into eight sectors and pond 37 into

four. The location of each observation of an individual at these 54 ponds was recorded. Table 12 lists the number of different sectors visited by 107 males observed two or more days at pond 36 or pond

37.

Table 12. Records of Males Observed on Two or More Different Days at Ponds 36 and 37

Humber of Individuals Pound in

One Two Three Pour Pond 36 Sector Sectors Sectors Sectors Total

Observed two days 13 48 61 Observed three days 2 8 7 17 Observed four days 1 3 1 5

Total 15 57 16 1 8 3

Pond 37

Observed two days 12 6 18 Observed three days 2 1 3 Observed four days 1 1 2 Observed six days 1 1

Total 15 9 24

The dragonflies at pond 37 were usually found in one of the two sectors containing the most vegetation. At pond 36, which had abundant vegetation in all sectors, most individuals appeared

successively in several different locations. Only two of the 83 males at pond 36 were in the same sector more than twice and only

15 were observed in only one sector. As long as the pond contains

many breeding sites there seems to be no marked tendency for males

of E. simplicioollis to return to a particular part of the pond on

different days. 55 a*. A male in a given appearance at a pond restricts its flight to a particular small section of the pond as described in the previous section. This localization is usually quite obvious and quite definite. It is also quite temporary, and lasts only until the individual is displaced by another dragonfly. When males were numerous at a pond and interactions were frequent an individual rarely maintained a specific flight area longer than 15 or 20 minutes. The longest time a marked individual was observed flying over one particular site was one hour and forty-three minutes.

This occurred on a fairly oool day when relatively few males were present. The marked individual participated in interactions with other males only five times. It left the area after the last interaction and was seen about an hour later in another sector on the opposite side of the pond.

Displaced males did not always leave the pond. They fre­ quently took up a new flight pattern, agai becoming temporarily localized, but over a different part of t. •: pond. This new flight area was usually fairly close to the first and was often obtained after displacement of another male. Individuals were sometimes seen, over a period of several hours, in several different sections of the same pond. The longest recorded lapse of time between the first and last observation of a male at one pond, on the same day, was approximately four and one-half hours. 56

Reproductive Period of Females

Non-pruinose Females at Ponds

Females observed at ponds were pruinose in 224 of the 335 records. One hundred eleven, about one-third, were non-pruinose.

Probably slight pruinescence was overlooked in some of these.

Several individuals were recorded at ponds twice, at intervals of one to four days, still not pruinose.

No difference could be detected in the behavior at ponds of fully pruinose, slightly pruinose and non-pruinose individuals.

Almost all of the non-pruinose females mated and oviposited during their appearanoes at ponds.

Movements to Ponds

Recoveries of females include 145 observations (139 indi­ viduals) at ponds that were preceded by a record away from ponds.

These movements by females to ponds are listed in Table 13. The first two columns list 126 females which were not pruinose at the time of the observation away from ponds. Sixty-nine of these re­ mained non-pruinose and 57 became pruinose during the interval be­ tween the two observations. This includes females marked during the maturation period and also those in the earlier part of the reproductive period. Presumably this group corresponds in age range to the males in the first two columns of Table 8. The last two columns of Table 13 list movements to ponds by pruinose females inoluding 13 records of individuals which were pruinose before the first recorded pond appearance and returns of six of the individuals 57

Table 13. Movements of Females to Ponds

Number of Movements

Females which were not Pruinose Both Observations8, Pruinose Females

To From From From From Pond Areas 1 - 6 , Areas Areas 1-6, Areas Number 14, 15 7 - 1 0 14, 15 7 - 1 0

37 5 7 2 1 36 86 18 11 5 35 6 34 2 33 2

Total 101 25 13 6

individuals remaining non-pruinose or changing from non- pruinose to pruinose5 number of each is given in text. in the first two columns after an intervening record away from ponds. Table 14 analyzes movements to ponds 36 and 37.

As in the case of males, most of the females in areas 1 to

6, 14, and 15 prior to pond appearances moved to pond 36. The

total percentage of movements from these areas to pond 37 (6.73 per cent) was almost exactly the same as that of males (Table-'*?) •

Also, most of the females from areas 7 to 10 crossed to pond 36.

The total percentage of movements from these areas which involved

crossing the woods was 74*19 per cent compared to 76.60 per cent

in males.

The percentages of females moving from one side of the

woods to a pond on the opposite side are higher in the pruinose 58

Table 14* Movements of Females to Ponds 36 and 37

Color When Observed Away from Non- Pond Pruinose Pruinose Total

Number 36 86 11 97 Moving Movements to from Pond 37 5a 2a 7a Areas 1-6, Per Cent Crossing Woods 5.49 15.38 6.73 14, 15 Total 91 13 104

Number 36 l8a 5a 23a Moving Movements to 1 8 from Pond 37 7 Areas 7 - 10 Per Cent Crossing Woods 72.00 75.00 74.19

Total

Moving across woods. group than in the younger females. The corresponding groups of blue males showed the lowest per cent of movements across the woods. The percentages crossing in the younger group of females are lower than in the corresponding male groups. The sample of pruinose females is rather small but these records seem to indi­ cate an increased tendency in females for movement to distant ponds in the later part of the reproductive period. There appears to be a fairly strong tendency to move to a nearby pond at the beginning of the reproductive period. Again the local conditions, lack of breeding sites at pond 37, probably resulted in greater movement from area 7 to 10 to pond 36. 59

Eleven marked females reached ponds 33* 34* and 35. All hut one of these oame from areas 1 to 5. As in the case of males, more females from these areas moved to ponds 33 to 35 than crossed to pond 37* No marked females were recovered at pond 32 or any of the other outlying ponds.

Movements from Ponds to Areas Away from Ponds

Twenty-three females were found in areas away from ponds after a preceding pond record. Ten of these moved from pond 36 to adjacent areas and five were in areas 7 to 10 after a record at pond 37. Pour crossed to areas 7 to 10 from pond 36 and two moved from pond 37 to areas 2 and 3. One female seen at pond 35 was later in area 5 and one marked at pond 32 was found in area

1, 16 days later.

Movements Between Areas Away from Ponds

Since females spend only a "brief time at ponds most records of females were obtained away from ponds and most of the movements between successive observations of individuals were from one field area to another. Table 15 analyzes 806 movements of females be­ tween areas away from ponds. The first row of the table contains

98 movements in whioh the female was pruinose both observations or became pruinose in the interval between observations. The second row lists 708 movements by non-pruinose individuals. This group probably is composed largely of maturation period individuals but it also contains early reproductive period females. As in Table

10* which analyzed male movements in a similar manner, each recovery 60

Table 15. Movements of Females Between Areas Away from Ponds*

From Areas From Areas 1 - 6 to 7 - 10 to Color of Areas Areas Areas Areas Females 1 - 6 7 -10 1 - 6 7 -10 Total

Pruinose one 46 8* 31* 13 98 or both 61.91 38.09 40.26 59.74 observations

Non-pruinose 491 16* 59 142 708 both obser­ 89.87 10.13 10.53 89.47 vations

Total 537 24* 90* 155 806 86.60 13.40 14.35 85.65

®The upper figure in each entry is the number of move­ ments and the lower is the percentage of the total from that area.

Movements across woods.

is counted as one movement and an individual is included several

times if it was observed more than twice successively in areas

away from ponds.

The movements of females in areas away from ponds show

about the same per cent crossing the woods from areas 1 to 6 as

from areas 7 to 10 in the total movements and in both subdivisions.

The percentages crossing in females which were pruinose one or both

of the observations are almost four times those of non-pruinose

females. This indicates increased movement about the areas away

from ponds during the later part of the reproductive period. The

total percentages crossing and the percentages of non-pruinose fe­

males crossing are very close to the corresponding percentages of 61

males (Table 10). The group of older females, in the first row of

Table 15, shows higher percentages of movements across the woods

than the group of older males (Table 10, first row).

Localization

A total of 263 individuals were recorded (marked or re­

covered) at ponds as shown in Table 16.

Table 16. Records of Females at Ponds

Total Individuals Individuals Reoords at Two Ponds

One day at pond 212 212 Twordays at ponds. 39 78 4 Three days at ponds 8 24 2 Four days at ponds 2 8 Five days at ponds 1 5 Eight days at ponds 1 8 1

Total 263 335 7

Seven of the 51 individuals seen at ponds on two or more

different days were found at two different ponds. Four of these

moved from pond 37 to pond 36, two from pond 36 to pond 371 and

one from pond 34 to pond 35* The individual which was seen on

eight different days at ponds was marked and recovered once at

pond 37 and after two intervening records in area 10 appeared at

pond 36 on six different days. The last record was 65 days after

it was originally marked. The longest interval between the first

and last records of an individual at a given pond was 54 days. 62

Female E. simplioicollis, as well as males, appear to generally become localized at a particular pond, but the proportion appearing at more than one pond was greater than in males. Since females remained at ponds only briefly, many appearances of marked females at ponds were probably not observed. Females seem to move about in areas away from ponds more than males during the repro­ ductive period and-probably the tendency to return to the same pond is less pronounced than in males. If conditions at pond 37 bad been more suitable for oviposition more females would probably have been observed there. Females were usually fairly abundant

in areas 7 to 10 but few were seen breeding at pond 37*

Table 17 summarizes the number of different sectors visited by females appearing more than once.at pond 36 or pond 37* Most

of these individuals were seen in more than one sector. No marked

female was observed at a pond twice on the same day. During one

appearance at a pond a female almost always remained in one small

area of one sector unless many males were present and there was

considerable interference with oviposition. In this situation the

female sometimes moved or was chased into other parts of the pond. 63

Table 17. Records of Females Observed on Two or More Different Days at Ponds 36 and 37

Number of Individuals Found in

One Two Three Four Pond 36 Sector Sectors Sectors Seotors Total

Observed two days 10 22 32 Observed three days 3 3 6 Observed four days 1 1 2 Observed five days 1 1

Pond 37

Observed two days 1 1 2

Total 11 26 5 1 43

Mating

The appearance of a female at a pond usually resulted in mating and oviposition. Sometimes females appeared briefly at pond edges and then left without mating. Late in the summer very old pruinose females, with the black color pattern almost wholly obscured and often with badly torn wings, were frequently found at pond edges. Only a few of these were observed in copulation or in the act of oviposition.

When a female arrived at a pond it flew low over the sur­ face often resting briefly on the shore or on an algal mat. Fe­ males almost always flew over areas containing floating vege­ tation. Sometimes a female would make a few dips of the abdomen

in the water in the same manner as when ovipositing. 64

If a male was present the female was usually seized in tandem almost immediately. Males always coupled with flying fe­ males. A resting individual was invariably ignored by males even though they passed quite closely by.

After the male had grasped the head of the female with its posterior abdominal appendages, the tandem pair usually assumed the copulatory position within a few seconds. This was accomplished by the female grasping the abdomen of the male with its feet and bending its abdomen forward bringing the eighth segment genital opening into contact with the second segment genitalia of the male.

Mating pairs usually settled into vegetation at the pond edge or dropped onto an algal mat. Sometimes a pair alighted while still in tandem but usually the oopulatory position was assumed while still in flight.

If another male were present in the vicinity it would often approach a mating pair and grasp at either the male or the female with its feet. Plying pairs were approached by other males more frequently than resting pairs. However, males were attracted to perched, copulating pairs and usually a pair disturbed by a second male took flight again. Once a male was observed alighting on the thorax of a male in copulo on an algal mat. It remained perched for several seconds and then flew; the mating pair did not fly.

If many males were present a mating pair usually remained in flight.

Several times males flying in copulo performed vertical circling movements with a second male without releasing the female. 65

Copulation usually lasted "between one and two minutes.

After the pair separated the female invariably dropped to floating algae or into shore vegetation and remained absolutely motionless for 45 seconds to about 2 minutes. Meanwhile the male would resume its flight pattern over the pond.

Oviposition

After the brief motionless period the female moved over the pond and began oviposition. The sites where eggs were de­ posited almost always were covered with floating vegetation or contained masses of Chara and other algae just below the surface.

In ovipositing, the female hovered over the site and re­ peatedly dipped the end of its abdomen in the water, with a quick tapping motion, releasing eggs with each dip. The eggs were usually placed in water over submerged vegetation, between float­ ing leaves, in small openings, or in water-filled depressions on an algae mat, but sometimes a female tapped its abdomen directly on emerged parts of a mass of algae. If undisturbed, females made about 125 to 200 dips within two or three minutes, moving about over a few square feet in the process.

If a female were captured during the interval between copulation and oviposition and its abdomen placed in water it would release eggs for a minute or more. Eggs were collected in this manner 24 times from 22 different females. The number of eggs ob­

tained ranged from 83 to 879 with a mean of 323*16. The two females 66 from which eggs were collected on two different days both yielded a smaller sample on the second occasion.

As soon as a female began oviposition movements the male which had previously copulated with it flew to the site and circled over the ovipositing female. This "guarding" behavior has been noted by several authors in several species of Libellulid dragonflies.

Other males in the vicinity were immediately attracted to an ovipositing female and would fly into the area engaging in very rapid interactions with the guarding male. Usually a single male would be repelled but when several approached, which was often the case, one of them would seize the female and the pair would copulate. Sometimes the first male was not particularly close to the female when oviposition began and in this case a second male often seized the female almost immediately.

After a second copulation the female again rested motion­ less for about a minute and then resumed oviposition, this time guarded by the second male. Again other males would dash in and frequently a third copulation resulted followed by a continuation

of oviposition. Sometimes there was a fourth pairing and copu­ lation. In 6 of 41 observations of a series of three or four

copulations in which a marked male was involved the marked indi­

vidual mated twice with a given female. These pairings were never

twice in succession. In each case after its first mating with the

female the marked male withdrew from the area after interactions with other males, returning when the female was ovipositing 6? following an intervening copulation. Often when three or four males were present, interacting over the oviposition site and grasping at the female, egg deposition was interrupted and the female left the pond after only a few oviposition dips.

Typically a female left the pond, either after a number of oviposition movements or when pursued by males, by rising high in the air, almost straight up, and flying directly away from the pond. Males would follow a female a short distance and then return, resuming their flight patterns over the surface.

Most mating and oviposition occurred during the middle of the day, usually the warmest part, from about 10:30 A.M. to

3:30 P.M. On cloudy overcast days very few individuals of either

sex approached the ponds unless the temperature was very high. In

1959, during a week of very hot (90° to 100°F), hazy, overcast

days dragonflies were very aotive at the ponds even though there was very little direot sunlight. Males tended to arrive earlier -

in the morning than females and were usually found at ponds later

in the afternoon.

Except during the early morning, late afternoon, and on

cool days, many males were present and a female rarely completed

oviposition without at least~two copulations. A single mating

and undisturbed oviposition seems to be the exoeption rather than

the typical situation in this species. Repetition of Oviposition

In central Ohio E. simplioicollis "begins mating activity in late May and continues until early September. A few adults were present at ponds until the first week of October in i960 but no oviposition was observed after September 12.

Forty-four of the 51 marked females found at ponds more than one day were seen ovipositing more than once. Two repeated on four different days, nine on three days and 33 on two days.

The time elapsed between successive recorded ovipositions ranged from 1 to 34 days with a mean of 12.2 days.

The females marked the day of emergence were later seen ovipositing} five were observed once, three twice, and two three times. The earliest record of oviposition was eight days after emergence and the latest 49 days. Other females were seen ovi­ positing up to 58 days after being marked. A total of seven indi­ viduals were observed ovipositing more than 40 days after they were first marked. The reproductive activity of E. simplioicollis females can apparently extend over a period of at least 50 days.

Egg samples were taken from five females which were ovi­ positing 41 to 57 days after being marked. In these five samples

35.82 per cent of the eggs hatched. In 15 egg samples from females captured 1 to 20 days after first marked 72.17 per cent of the eggs hatched. This indicates decreased viability in eggs of older females. 69

Sex Ratio

Males of most species of Anisoptera appear to be more numerous than females because they are generally more in evidence and spend considerable time flying over breeding areas. Males of most species of Libellulids far outnumber females at ponds. In a few studies the comparative abundance of, the sexes has been de­ termined by counts of nymphal exuviae or of teneral individuals and in Anisoptera the ratio of males to females has been almost

111, with females slightly in the majority.

Tiensuu (1935) oollected the exuviae of emerged nymphs of

Oordulegaster boltonii, a European species. He found 44*1 per cent males and 55*9 per cent females. Corbet (l95l)» from collection of the exuviae of a European Aeschnid, Anax imperator, found 48.96 per cent males and 51*04 per cent females. Jacobs (1955) marked

338 teneral Plathemis lydia. 129 of which were males and 209 fe­ males, a ratio of 1 male to 1.62 females. Kormondy (1959) col­

lected exuviae of Tetragoneuria oyanosura and obtained 110 males

and 159 females.

The sex ratio of E. simplicicollis is probably closely

indicated by counts of newly emerged individuals. Hew tenerals, "

captured at pond edges, show no differential behavior which would

lead to capture of more of one sex than of the other. During the

two seasons of this study a total of 529 newly emerged individuals

were captured and marked. Two hundred thirty-four (44*42 per cent)

were males; 294 (55*58 per cent) were females; a ratio of 1 male to

1.25 females. Females comprised 57*89 per cent of the total marked. 70

This higher proportion of females was probably due to their being

muoh easier to catch when fully mature than males.

length of Adult Life

The longest lapse of time from the day of emergence to a

recovery was 60 days in females and 54 days in males. One male

marked during its maturation period was also recovered 54 days

after marking and another was found 63 days later. Five females

marked sometime after the day of emergence were found 62 to 68

days later. The mean time elapsed from marking to the last re­

covery of the 619 females was 12.15 days; to the last recovery of

the 513 males, 10.95 days.

Females seem to survive longer than males. Only three of

17 individuals found more than 50 days after being marked were

males. Twenty-six (5*26 per cent) of the males and 61 (9*85 per

cent) of the females were found more than 30 days after first

captured. In addition to these recoveries, in late August and in

September of i960 several old females were found with parts of the

marked wings torn away. Although the individuals could not be

identified the color of the markings indicated that they had been

marked before July 6. The last individuals seen in October were

females.

Food of Adults

Most of the Anisoptera are not particularly selective in

food habits (Brues, 1946; Wilson, 1920). They generally take as

prey a considerable variety of smaller insects and predominance of 71 one kind of prey usually is a result of its great abundance in areas frequented by feeding dragonflies®

Most of the feeding activity of E. simplicicollis occurred in the field areas away from ponds. Pour males were seen leaving ponds with a captured damselfly and one was seen with a large

Tabanid. Dragonflies flying slowly about or perched in low vege­ tation tended to dart at any insect moving past including large species which were never taken as prey. They would also dart at wind blown leaves or seeds, or at a piece of paper swung on a string. There was nearly always a response to movement of any sort by a relatively small object. Location of prey seems to be a result of visual stimulus.

Adult E. sinrplicioollis oapture prey, in flight, by quickly darting at the insect and seizing it with mouthparts and legs. The prey was not eaten while flying; the dragonflies perched almost immediately. No B. simplicicollis were seen perched flat on bare ground or on logs while feeding although mature individuals often rested on such sites at other times. They usually held onto a plant stem with the two hind pairs of legs while manipulating the prey with the prothoracic legs and the mouthparts. Five or 10 minutes usually were occupied in the consumption of a single insect. Wings of prey, particularly of Lepidoptera, were usually not eaten.

Individuals which were watched continuously in areas away from ponds made successive captures of prey at intervals of 3 to

24 minutes, timed from cessation of mastication of the first catch 72 - to seizing of the next. The prey of 232 individuals is given in

Table 18. The smallest insects taken were Cercopids and Doli-

chopodids; the largest were Pierid butterflies.

Table 18. Prey of Adults

• Per Sent Sub­ Total Records of Total Order totals for Each Order Records

Ephemeroptera 1 .43 sub-imago mayfly 1 Odonata 15 6.47 Zygoptera Argia apicalis 1 Enallagma civile 5 Enallagma geminatum 2 Enallagma signatum 1 Ischnura verticalis 6 Orthoptera 1 .43 Tettigoniidae, long horned grasshopper nymph 1 • Homoptera 23 9.92 Fulgoridae 1 Cioadellidae, leafhoppers 7 Cercopidae. froghoppers 15 Diptera 138 59.46 Tipulidae, cranefly 1 Tabanidae Chrysops sp. 67 Tabanus sp. 1 Dolichopodidae 7 Syrphidae 11 Tachinidae 4 Calliphoridae 6 Sarcophagidae 5 unidentified Muscoids 36 Lepidoptera 51 21.96 Pieridae 9 Lycaenidae 2 Pyralidae 14 Geometridae 6 unidentified small moths 20 Hymenoptera 3 1.29 Ichneumonidae 1 Haliotidae. sweat bees 2 Total 232 100.00 73

Diptera and Lepidoptera comprised over 80 per cent of the observed prey. Williamson (1900) referring to E. simplicicollis stated "Diptera form the bulk of their food, many Ohrysops justly perishing in this way." In this study Ohrysops, deer flies, made up 48.55 per cent of the Diptera which were observed being taken as prey. Since Ohrysops are usually quite abundant in the vicinity of an observer the number seen captured is probably higher than the true proportion in the diet of the dragonfly. Williamson

(1900) also mentions Lepidoptera and Zygoptera as prey of E. simplicicollis. Wilson (1920) tells of seeing this dragonfly picking house flies off a window screen. He also captured an E. simplicicollis feeding on another dragonfly of its own speoies.

There appear to be no reports of these dragonflies preying on

Homoptera or Orthoptera, but these jumping insects made up about

10 per cent of the prey observed. The leafhoppers and froghoppers were captured in the air as they hopped by a dragonfly. I did not observe the capture of the single grasshopper; the dragonfly was already perched and feeding when first observed.

Enemies of Adults

Predators

Adult dragonflies are preyed upon by only a few animals and as far as is known none attack only a certain species. Several arthropods and vertebrates were observed feeding on dragonflies including E. simplicicollis. 74

The remains of Odonata, including three hlue males and one female of B_. simplicicollis were found in wehs of large Argiopid spiders. Once I saw a large Asilid fly, Promachus sp., seize a mature blue male E. simplicicollis. The Asilid, with its mouth­ parts, pierced the dragonfly back of the head and either killed or paralyzed it almost immediately. This robber fly was fairly abundant in the area studied. Ko larger dragonflies were observed preying on E. simplicicollis.

Green frogs, Rana olamitans, which were very abundant at the ponds studied, probably fed to some extent on dragonflies.

Only one was actually observed catching an B. simplicicollis. The dragonfly was an intermediate male.

Kennedy (1950) examined the bird stomach content records of the United States Pish and Wildlife service and reported on dragonflies as food of North American birds. Predation by birds is largely a result of the bird coming into contact with Odonata and generally dragonflies form only a small part of the food of a given bird species. Kennedy pointed out, however, that occasionally individual birds seem to show a preference for Odonata.

Almost all the breeding birds and several of the common migrants occurring in the area about the ponds studied were in­ cluded in Kennedy's list of species which had dragonflies in one or more of the stomachs examined by the Pish and Wildlife service.

The greater and the lesser yellowlegs, both of which appear in the area studied as migrants in July and August, had the highest count of any species. Over 20 per cent of the stomachs examined contained 75 dragonflies, both nymphs and adults. On several occasions in both

1959 and i960 I saw lesser yellowlegs and solitary sandpipers eating newly emerged E. simplicicollis at ponds 34 and 35. The emergence of E. simplicicollis reaches its peak at about the time these birds begin to return to central Ohio and predation on new tenerals may be quite high especially at shallow ponds frequented by shorebirds.

Crested flycatchers, eastern kingbirds, and belted king­ fishers also ranked high on the list of dragonfly-eating birds.

Both summers a kingbird was present almost every day at pond 36, capturing dragonflies of several species. Wings of dragonflies, including E. simplicicollis, were sometimes found along shores.

Presumably these were the remains of bird attacks, probably king­ birds. Crested flycatchers were seen taking dragonflies three times, one of which was an E. simplicicollis. A pair of king­ fishers were constantly in the area but I never saw them capture dragonflies. Once a song sparrow was seen carrying a teneral

E. simplicicollis.

Weather and Injuries

Dragonflies, particularly new tenerals, are probably more adversely affected by hard rains than by attacks of predators. On two mornings in June, 1959» while collecting new tenerals along the shores of pond 36 after brief but heavy early morning rains,

I found dead teneral E. simplicicollis on the ground. Three were found on one day and four on the other. Several others were weakly 76 fluttering, entangled in wet grass. When picked out of the vege­ tation these oould fly or at least maintain a perch on a twig.

Dead dragonflies were rarely found otherwise and these presumably were victims of the earlier rainfall.

Adults often had small opaque spots on the wings which appeared to he rain damage. Several newly emerged tenerals were caught and their still soft wings sprinkled with water. These individuals were kept in large paper hags for several hours and as the wings hardened and dried they showed opaque marks similar to those found on the wings of other individuals.

A number of adults were found with injuries to the wings which apparently resulted from improper expansion at emergence.

Sometimes only the tip or one edge of the wing was bent or crumpled but a few individuals were found with one wing completely crumpled or not expanded at all. In two such cases the injured wing broke off completely in a few days. A three-winged individual did not seem to be particularly handicapped in its movements in the areas away from ponds. One blue male with about three-fourths of a hind wing gone, was seen at a pond. It remained only a few minutes, leaving after a brief interaction with another male. A female with one wing totally lacking was seen mating and ovipositing.

Individuals with torn wings were often found at ponds and late in the summer very battered specimens were rather common.

The wings of older individuals seemed to be quite brittle and probably were damaged by contact with twigs or other vegetation. 77

Also males sometimes come in physical contact with each other during interactions and striking against the hard "body of another dragonfly could break or tear wings.

A few individuals were found with the abdomen curved to one side. This could be another injury occurring at emergence.

All of these dragonflies were seen away from ponds. Such a mal­ formation would probably interfere with mating.

One female, which was captured at pond 37, exhibited a badly injured abdomen. The left side, from segments 5 "to 9 was mangled and crushed and was black in color. The whole abdomen bent to the left and the individual flew erratically. This could have been the result of an attack by a predator, possibly a bird.

Parasites

Odonata which breed in ponds and lakes are frequently

parasitized by larvae of Hydracarina, the water mites. These are usually species of Arrenurus. the largest and most widespread

genus of water mites. Adult mites identified to this genus were

abundant in pone 36. The adult mite and the second of the two

active immature stages are free swimming. The first immature

stage, a six-legged larva, is the form which is parasitic on

Odonata. The larva which has hatched in the water attaches to a

dragonfly nymph and when the adult emerges the mite migrates from

the nymphal exuviae to the teneral dragonfly and attaches to some

soft part of the body wall. It exists as an external parasite,

feeding on the insect's body fluids and greatly increasing in size. 78

The mite then enters a resting stage, called a nymphochrysalis or

a nymphophan, within an apoderm, an enclosing envelope. An eight­

legged- nymph emerges from the apoderm and must reach water. After

a period of free-swimming the nymph enters another resting stage

from which the adult mite emerges.

On newly emerged B. simplicicollis the mites appeared as

tiny, rounded, pale objects on the sternum of the abdomen or at­

tached to the pleural membrane under the ventral edge of the tergum.

Occasionally they were found on the thorax. By the second day

after emergence they were noticeably larger and were pale red in

color. In a week they became shiny reddish-brown and were about

1 mm. in diameter. The Nymphochrysalis stage was found on four

infested dragonflies which had been marked the day of emergence,

14, 18, 19, and 22 days after the dragonfly left the pond. This

stage of the mite was slightly larger than the full grown larva

and was dark brown in color.

This parasite was found on adult B. simplicicollis only

during the first part of summer. In 1959 "the last infested dragon­

fly was found July 16, and in I960, July 21. In 1959> 229 (22.72

per cent) of the 1,018 individuals marked from May through July 16

had mite infestations; in i960, 338 (22.12 per cent) of the 1,528

individuals marked through July 21 were infested. However, on some

days in June 70 to 80 per cent of the new tenerals marked had mites

attached.

One hundred eighty-one, 31.92 per cent, of the infested

individuals were recaptured at least once, compared to 36.92 per 79 oe^t recaptures of non-infested individuals. The infestation usually was not large; most individuals had from 2 to 30 mites

attached. On a few, however, the whole ventral surface of the abdomen was packed with several hundred mites. Dragonflies with a very heavy infestation sometimes had the abdomen curved downward

or to one side. The tergal portions were usually spread laterally.

The presence of so many of these parasites can interfere with mating. Twice a pair of E. simplicicollis were seen remaining in

tandem for four or five minutes and repeatedly failing to maintain

a copulatory position. The female in both cases was examined and

found to have a very heavy mite infestation which prevented its

abdomen from bending sufficiently for contact with the second seg­

ment genitalia of the male.

Thirty-seven of the marked individuals were recovered

totally free of mites, 8 to ^5 days after first marked. Four of

these had carried a heavy infestation estimated at over 200 indi­

viduals. The sternum of a dragonfly which had been infested was

usually scarred and if the infestation had been heavy the edges of

the tergites remained spread farther apart than usual.

The slightly lower recovery record of infested individuals

could be due to increased mortality. A large number of parasites

would probably decreases the activity and vitality of an individual

and render it more susceptible to adverse weather conditions and to

attacks of predators. The majority of the infested E. simplici­

collis. which had only a few mites probably were not greatly

affected by the presence of these parasites. Many of the old

females found around ponds in late sununer bore mite scars. 80

Recovery of Marked Individuals

Many marked individuals were never seen again after the

original capture and others were recaptured only once or twice within a few days after being marked. Probably many marked dragon­

flies were by ohance not encountered again since the area covered was fairly large and there was continuous movement by the dragon­

flies to and from the ponds. Others may have moved completely out

of the area although few marked individuals were recovered at out­

lying ponds. Again they could have easily been overlooked since

the outlying areas were visited at the most, once a week for one

or two hours. The remaining individuals probably were taken by

predators or did not survive periods of bad weather.

Table 19 summarizes recoveries of marked individuals. In

the case of males recoveries of individuals marked the day of

emergence, during the maturation period, and during the repro­

ductive period are listed separately. Only the recoveries of

females marked the day of emergence are listed separately sinoe

maturation and reproductive period females cannot definitely be

separated on basis of color.

In both males and females the percentage of reoovery in

individuals marked the day of emergence was lower than the total

reoovery percentage. This indicates either greater dispersal or

greater mortality in the first days of adult life. These indi­

viduals did show more local dispersal during the maturation period,

presumably in the early part, and soft-bodied weak flying tenerals 81

Table 19* Recoveries of Harked Individuals

During During Time Matu­ Repro­ of Ray of ration ductive Marking Emergence Period Period Total

Number 235 771 329 1335 Marked Males Numbc r 79 343 91 513 Recovered 33.62 44.49 27.66 3^.43 3 & t Number 294 1835 Marked Numb( r 80 Females 619 Reoovered Per 27.21 33.77 Cent

would be more susceptible to predation and to adverse weather. In males the highest recovery record was of those marked during the maturation period, indicating inoreased survival and decreased dispersal. The low recovery of individuals marked when fully blue is probably due to increased mortality in older males and to dis­ persal resulting from displacements at ponds. THE NYMPH

The nymphs of 5. simplicicollis, along with other species of Lihellulids, were found in submerged tangles of Chara and filamentous algae. They were particularly numerous in pond 36 and were easily collected by separating and shaking algal masses in a white enamel pan.

Food of Nymphs

The food of dragonfly nymphs, like that of adults, is varied and the predominant prey are usually the most abundant smaller animals with which the nymph comes in contact. E. simpli- oioollis nymphs kept in the laboratory would eat almost any of the small invertebrates present in pond 36 inoluding nematodes, various crustaceans, and many aquatic insects including immature Ephemer- optera, Odonata, Diptera, and Coleoptera. Newly hatched E. simpli­ cicollis nymphs were fed Paramecium which they oaptured easily, often seizing several with one snap of the labium. Second instar nymphs could capture and eat first instar mosquito larvae whioh were about as long as the dragonfly. Nymphs were attracted to movement and individuals kept in small containers and fed at inter­ vals would respond to any movement over the container prior to feeding. They are probably directed to prey by visual stimulus.

82 83

Predators

Odonata nymphs serve as prey for many larger aquatic in­ sects including other larger dragonflies of their own and other species. Kennedy (1950) reported Odonata nymphs listed hy the records of the United States Fish and Wildlife Service in the stomach contents of ducks, herons, and shorebirds. Baker (1916) mentions finding numerous dragonfly nymphs in the stomachs of painted turtles. Fish are probably the greatest predator of

Odonata nymphs. Analysis of stomaoh oontents of small pond- raised game fish has shown a high oontent of Odonata nymphs in almost all the fish examined (Wilson, 1920). Dragonflies seemed to provide such an important food source that Wilson recommended

stocking new fish ponds at hatcheries with Odonata by oolleoting eggs and placing them in the water.

All the ponds in the Delaware Reservoir Wildlife Area are

stocked with game fish, mostly bass and bluegills. Pond 36 had a

substantial population of bluegills which could be seen in large

schools in the clear deep water near the dam. Although the pond was fished regularly they were still quite abundant at the end of

summer. These fish were probably a major predator of E. simpli-

oicollis and the other dragonfly nymphs in the pond. The habits

of the dragonflies appear to provide some protection from fish.

The nymphs were usually found within tangles of submerged vege­

tation in shallow parts of the pond. 84

Duration of the Nymphal Period

Ten samples of 50 nymphs vere collected in the same sector of pond 36 at different times of the year from April to November,

1960. An additional sample of 37 was oolleoted in February of

1961. The total length of eaoh individual was measured with a binocular microscope and a calibrated ocular grid. Except for the last three samples the nymphs were returned to the pond the fol­ lowing day. Figure 20 shows histograms of the number in each

sample falling into four size olasses. According to Bick's (1941) measurements of reared E. simplicicollis, nymphs in approximately the first four instars would fall into class A, under 2.0 mm.)

class B (2.0 to 6.0 mm.) would include instars 5 through 8; class

C (6.0 to 10.0 mm.) would inolude instars 9 through 11j class D

(over 10.0 mm.) would include the last one or two instars before

emergence. Biok succeeded in rearing only one individual through

emergence as an adult, which occurred after 13 nymphal instars.

On the basis of morphological characters he considered it possible

that some individuals might transform earlier than the thirteenth

molt.

The data from measurements of nymphs showed that from

October to April most of the nymphs were in the two middle size

ranges with a slight increase in the proportion of the larger of

the two groups. The proportion in class D, the last one or two

instars, increased from April to the July 1 sample after which it

dropped off sharply although at least one individual over 10.0 mm.

was found in all samples. No nymphs under 2.0 mm. were found in 8§

FIGURE 20 LENGTHS OF NYMPHS IN SAMPLES

A. UNDER 2 . 0 MM. C. 6 . 0 TO 10 . 0 MM. B. 2.0 TO 6 .0 MM. ft OVER 10 MM.

A B C D AO CD A B CO ABCD APRIL 9 , I9 6 0 MAY 1,16 6 0 MAY 2 5 , 19 6 0 JUNE 15,1960

$ 9 0 .

£20 oio

AO C D A B C D ABC D A BCD JULY I, I9 6 0 JULY 2 2 , I9 6 0 AUO. 10,1960 SEPT. 1,1960

g9-20 ' •' 9 ' '

15 > 0 * 0 i

d« z ----1 ABCD A B CD A B CD OCT. 4 , I9 6 0 NOV. IT, I9 6 0 FEB. 24,1961 8.6 samples prior to June and the proportions then increased through the summer dropping off in September and October* One individual measuring 1*8 mm. was found in November*

These data indicate that the E. simplicicollis nymphs pass the winter in the middle instars. In the spring there is an in­ crease in the proportion of larger nymphs as growth is resumed.

The peak abundance of large nymphs occurred in June and in early

July prior to the peak periods of emergence. Meanwhile, beginning in June, there was an inorease in the number of very small nymphs, indicating appearanoe of the offspring of the I960 adults. By

September and Ootober most of these had apparently reaohed the

second or third size group.

Bick (1941) reared E. simplicicollis from hatching to trans­ formation in 113 days (123 days from oviposition). The individual which successfully emerged spent 55 days in the last two instars.

A sizable proportion of the nymphs collected in this study were

still in the middle size ranges in May and June yet most seem to

have transformed by the end of July. This indicates that the time

spent in the final instars may be shorter than in Bick*s reared

material.

The interval between the earliest observed oviposition

(May 31, I960) and the latest observed new teneral (September 1,

i960) was 93 days. Even if the final instars are shorter than

indicated by Bick it seems unlikely that nymphs from early season

matings transform the same year. If any sizable number of the

early hatching nymphs reaohed maturity during the summer there 87 should be an increase in the proportion of the last two size ranges during mid and late summer. However, there is no inorease in class C until October, a month after the last emergence was ob­ served and individuals in the final instars are soaroe after July.

In central Ohio, if both late spring and early fall were warm, so that oviposition began early and nymphal growth continued until late, a few individuals presumably might emerge within a single flight season. However, there is no indication, in either nymphal measurements or in the emergence pattern of adults, that two broods generally occur.

The majority of the nymphs fell into two widely separated size groups only in the July first sample which apparently con­ tained an overlap of generations. There was a regular increase and decrease in the proportion of eaoh size group over the year, with each class reaching a peak in succession. This indicates that nymphal development is completed within one calendar year.

Corbet (1954, 1956) has classified British dragonflies into two general categories according to the type of life history.

Spring species have a diapause in the last nymphal instar which results in synchronized emergence during a short period early in the season. Summer species do not have a diapause and enter the final instar shortly before emergence. The period of emergence is thus lengthened and the peak is not at the beginning of the emerg­ ence period. E. simplicicollis appears to fit Corbet's definition of a summer speoies. DISCUSSION

Dispersal

The recapture data in this study indicated little dispersal except for the high percentages of movements away from pond 37 and the surrounding areas. The recaptures of two males at pond 32, one male at pond 38, and the movement of a female from pond 32 to area 1 showed that E. simplicicollis move up to approximately half a mile. Undoubtedly the range of dispersal is greater than directly indicated by these reoaptures. E. simplicicollis occurs on the

Bass Islands in Lake Brie, five miles from the mainland and there * it is found on different islands in ponds several miles apart

(Kennedy, 1922)•

In a locality like the Delaware Reservoir Wildlife Area, where suitable breeding sites are abundant and close together, the amount of local dispersal by E. simplicicollis probably remains

small. Individuals tend to remain near the pond from which they

emerged, they tend to return to that pond during the reproductive period, and they tend to become localized and subsequently return

to the same pond throughout the reproductive period.

In central Ohio, E. simplioioollis is found at almost any well vegetated, shallow body of standing water. A single pair

reaching a new pond could presumably populate the area. In the

absence of interference with oviposition by extra males, a female 88 89 would probably deposit a maximum number of eggs. The offspring of individuals reaching a new pond the first season would tend to remain at that pond the next season and a sizable population oould result in a few years.

Away from ponds E. simplicicollis tends to fly slowly about in vegetation and dispersal probably results from wandering by feeding individuals, between pond appearances, over areas between two ponds. In the initial flights of tenerals and in the flights of females and displaced males away from pond considerable distance may be covered and these flights probably contribute to dispersal.

There is considerable dispersal on a very local basis as evidenced by the appearance of males in several sectors of a given pond on the same and on different days. This appears to be a direct result of male interactions and consequent displacements.

Functions of Some Aspects of Behavior

Because of the tendenoy of male dragonflies to remain for

considerable periods of time at ponds a differential sex ratio, with males far outnumbering females, exists at the breeding sites,

although the true sex ratio may be approximately 1:1. Jacobs (1955)

has pointed out that spacing of dragonflies by male interactions

alleviates this condition and as a result some of the interference

with oviposition is eliminated. In E. simplicicollis the various

interactions do result in spacing of males about a pond and the

guarding action of a male over an ovipositing female to some extent

further repels additional males. 90

The behavior of the female following copulation also ap­ pears to he a behavior adaptation which to some extent prevents male interference with oviposition. Apparently males oannot see or at least are not attracted to a motionless female and during the period a female remains still, males in the area, which were previously attracted to the copulating pair, return to their former flight areas or enter into interactions which result in the displacement of one or more of them. Thus when the female begins oviposition the number of males in the vicinity is likely to be

considerably smaller than immediately after copulation.

In spite of these behavior mechanisms, oviposition at pond 36 was frequently interrupted and a given female often com­ pleted only a few oviposition movements during its entire appear­

ance at the pond. At other ponds, where males were less closely

spaced, usually a female still oopulated two or three times but

interruptions of oviposition were less frequent and a large number

of dips usually were accomplished. Rarely was the entire process

disrupted completely. Conditions at pond 36 actually may have

been overcrowded in regard to the B. simplicicollis population.

In this situation the frequent interruption of oviposition may

function in preventing further overcrowding of nymphs developing

in the pond.

Multiple copulation of females with several different

males at each pond appearance increases the probability that a

given female will mate with a given male during the course of the

reproductive period. The tendency of individuals to return to a 91

different part of a pond at different appearances and the oontinual

displacements and dispersal of males also increases this proba­ bility. Thus even though E. simplioioollis tends to spend itB reproductive period in fairly limited locality, breeding at one

particular pond, the effective breeding population is large. In

such a population genetio variability is preserved and gene fre­

quencies remain relatively constant. Repeated copulation also may

result in more complete fertilization of eggs.

Territorialism

Territorialism has received the most attention in birds

and most of the definitions and explanations of this phenomenon

have been developed by students of bird behavior. So many vari­

ations and exceptions were observed in territorial behavior that

the definition of territory was finally reduced to "any defended

area" (Noble, 1939). With this general definition the concept of

territorialism can be applied to a wide variety of situations in

both vertebrate and invertebrate behavior with a separate consider­

ation of function and motivation in regard to each particular oase.

Moore (1952) objected to considering the behavior of male

dragonflies occupying a restricted area as true territorialism

because his experiments indicated that the males oould not dis­

tinguish sexes and to a lesser extent species and therefore ap­

proached other males because of sexual attraction and not because

of aggressive behavior. He considered dispersal the primary function

of clashes between males. Jacobs (1955)» however, considered the 92

spacing and interactions of males to be territorial behavior, as defined by Noble, and in the case of Plathemis lydia and Perithemis tenera, with the function of prevention of male interference with oviposition. Kormondy (1959) considered mere occupancy of an area to be a passive expression of defense of territory.

As discussed above, in E. simplicicollis. male interaction

and spacing does reduce interruption of oviposition unless males are extremely abundant at a given pond. Males of E. simplicicollis

appear to discriminate between males of their own and other species

either by appearance or by response of an approached male. There

seemed to be oomplete discrimination between females of their own

and other species. No E. simplicicollis male was observed ap­

proaching or undertaking coupling actions with a female of another

species including Pachydiplax longipennis the next most abundant

species and the female most closely resembling that of E. simpli-

oicollis. The rather elaborate patterns of male interaction in

E. simplicicollis. particularly the vertical circling movements,

are difficult to explain on the basis of sexual attraction since

no similar movements are performed by males toward females.

I therefore consider the localization and spacing, main­

tained by interactions, of male E. simplicicollis at ponds to be

territorial behavior of a transitory nature, under the general

definition of Noble, as applied to Odonata by Jaoobs. The primary

function of this territorialism appears to be prevention of dis­

ruption of oviposition although local dispersal probably is a

secondary function. The latter,, by continual redistribution of 93 males, results in maintainence of a large effective 'breeding population. The secondary function thus seems to counteract one of the results of the primary function* limitation of effeotive breeding population by expulsion of males which would otherwise have mated with a given female.

St. Quentin's (1934) original interpretation of Odonata territories as "jagdreverien" or hunting grounds does not seem applicable to E. simplioioollis since these dragonflies rarely captured prey over their pond areas and there were no indications away from ponds of feeding by individuals in a restricted area from which other individuals were expelled. SUMMARY

During the summers of 1959 and I960, 3,170 adults of a

Lihellulid dragonfly Erythemis simplicicollis were marked and re­ leased. One thousand one hundred thirty-two of the marked indi­ viduals were recovered a total of 1,838 times. In addition to the study of marked individuals, observations and investigations were made of other phases of the biology of this species. The major results and conclusions of this study are as follows:

1. Emergence began in late May and continued until the first of September. Peak periods of emergence occurred in early

June, at the end of June, and in the third week of July.

2. After emergence and prior to the beginning of repro­ ductive activity adults underwent a maturation period of a week or more in duration, during whioh they remained away from ponds.

3. The extent and intensity of the black color pattern of females and teneral males varied considerably and often changed in a given individual, becoming darker and more extensive during the maturation period.

4* Males became wholly dull blue in color 8 to 12 days after emergence. A period of intermediate ooloration between green-black and blue began 6 to 11 days after emergence and lasted one or two days. Females became slightly pruinose 8 to 17 days after emergence. 94 95

5. During the maturation period most individuals remained in the same general area and most movements seemed to occur in the early part of the maturation period.

6. A few males appeared at ponds while stillin inter­ mediate coloration. Both pruinose and non-pruinose females were found at ponds.

7» In movements to ponds a high percentage of both males and females in the areas adjacent to pond 36 appeared at that pond.

A high percentage of both males and females in the areas adjacent to pond 37 moved across the woods to pond 36. This apparently was a result of lack of breeding sites at pond 36. Three marked males were recovered at outlying ponds.

8.. In movements between areas away from ponds older females

showed greater movement than younger females and than the corre­

sponding group of males.

9. Most individuals tended to return to the same pond on

successive days. A higher proportion of females than males were

recorded at two different ponds.

10. On successive records at ponds there was little tend­

ency of either sex to return to one particular sector of the pond.

11. Males at ponds became temporarily localized and flew

in a definite pattern over a restricted area.

12. Males upon encountering one another at ponds performed

a series of interactions composed of parallel flights and vertioal

circling. Interactions sometimes ended in a vertical flight. The 96 series of interactions terminated when one male withdrew or was displaoed. Interactions were wholly intraspeoifio.

13. Hating occurred at ponds and a pair in copulation sometimes remained in flight. Other males were attracted to a mating pair.

14• After copulation a female perched and remained motion­ less for a period of one or two minutes.

15. If the male which had copulated with a female was still in the vicinity when oviposition "began it would circle over the female in a "guarding" movement.

16. Males were attracted to ovipositing females and in spite of interactions with the guarding male another male usually seized and copulated with the female. Most females copulated two or three times during a single appearanoe at a pond.

17. Localization and spacing of males at ponds was con­ sidered territorial behavior. The primary function of this ter- ritorialism appeared to be prevention of male interruption of oviposition.

18. Females were capable of produoing up to 879 eggs at one pond visit although the number in colleoted samples varied considerably. The mean number of eggs obtained from females caught after oopulation but before oviposition began was 323*16. Females were seen ovipositing up to 58 days after first marked. Indi­ viduals were reoorded repeating oviposition one to three times.

19. In collections of newly emerged individuals the sex ratio was 1 male si. 25 females. 97

20. Males can live as adults at least 63 days and females at least 68 days. In general females seemed to survive longer.

21. Most of the feeding aotivity of adults occurred away from ponds. Diptera and Lepidoptera formed the hulk of the prey oaptured.

22. Predators of adults observed included spiders, Asilid flies, frogs, and birds. Migrating shorebirds in July and August, feeding on new tenerals, are probably the greatest predator.

23. Approximately 22 per cent of the individuals marked

prior to mid-July were infested by ecto-parasitic larvae pre­

sumably of Arrenurus sp», water mites.

24. Collections and measurements of nymphs showed that

most individuals overwintered in the middle \nstars. There was

no evidence of two generations emerging within one flight season

or of more than one calendar year being spent in the nymphal stage.

There was an overlap of generations in July.

25. Erythernia sinrplioicollis fits Corbet's definition of

a summer species of Odonata. LITERATURE CITED

Baker, Frank C. 1916. The relation of Mollusks to fish in Oneida Lake. Technical Publication No. 4, New York State College of Forestry of Syracuse University, pp. 8 -366.

Biok, George H. 1941* Life history of the dragonfly Erythemis simplioioollis. Ann. Ent. Soc. Amer. 34(l)*215-230.

Borror, Donald J. 1934. Eoological studies of Argia moesta Hagen (Odonata* Coenagrionidae) by means of marking. Ohio Jour. Sci. 34(2)*97-108.

Brues, Charles T. 1946. Insect Dietary. Harvard Univ. Press, Cambridge, Mass. 466 pp.

Byers, C. Francis. 1930. A contribution to the knowledge of Florida Odonata. Univ. of Florida Pub., Biol. Sci. Ser. 1(1)*9-327.

Corbet, Philip S. 1951* The emergence and sex ratio of Anax imperator Leach (Odonata*Aeshnidae). Ent. Monthly Mag. 871174-179•

______. 1952. An adult population study of Pyrrhosoma nymphula (Sulzer) (OdonatasCoenagrionidae) Jour. Anim. Ecol. 21* 206-222.

1954. Seasonal regulation in British dragonflies. Nature 174*655*

- 1956. The life histories of Lestes sponsa (Hansemann) and Sympetrum striolatum (Charpentier) (Odonata). Tijdschrift Voor Entomologie 99*217-229.

______1957. The life history of the emperor dragonfly Anax imperator Leaoh (Odonata*Aeshnidae) Jour. Anim. Ecol. 26>t 1-69.

Jacobs, Merle E. 1955. Studies on territorial Asm and sexual selection in dragonflies. Ecology 36(4)*566-586.

Kennedy, Clarence H. 1922. The ecologioal relationships of dragon­ flies of the Bass Islands of Lake Erie. Ecology 3(4)* 325-336. 98 99

Kennedy, Clarence H. 1923* The phylogeny and the Geographical distribution of the genus Erythemis (Odonata). Univ. of Mich., Mus. of Zool. Misc. Pub. No. 11, pp. 19-23.

______. 1950. The relation of American dragonfly-eating birds to their prey. Eoologioal monographs 20(2)1104-142.

Kormondy, Edward J. 1959. The systematios of Tetragoneuria based on ecological, life history, and morphological evidence (OdonatatCorduliidae). Univ. Mich. Mis. Zool. Misc. Pub. No. 107> 79 PP*

Moore, N. W. 1952. On the so-called territories of dragonflies , (Odonata*Anisoptera). Behavior 4*85-99*

Needham, James G. and C. Betten. 1901. Aquatic insects in the Adirondacks. Bull. New York State Mis. 47*383-612.

Needham, James G. and Minter J. Westfall, Jr. 1955* A Manual of the dragonflies of North America (Anisoptera). Univ. of California Press, Berkeley and Los Angeles xii, 613 pp.

Noble, G. K. 1939* Symposium on the individual vs. the species. IV. The role of dominance in the social life of birds. Auk 56*263-273.

St. Quentin, B. 1934* Beobachtungen und Versuche an Libellen in ihren Jagdreveieren. Konowia 13*275-282.

Say, Thomas. 1839* Descriptions of new North American neuropterous insects and observation on some already described. Jour. Aoad. Nat. Sci. Philadelphia 8i2-46.

Tiensuu, L. 1935* Uber die Lebensweise und Proportionale Anzahl der verscheidenen Geschlichter eineger Odonaten. Ann. Soc. Zool.-Bot. Vanamo 3*1-17*

Williamson, E. B. 1900. The dragonflies of Indiana. Ind. Dept, of Geol. and Nat. Res. 24th Ann. Report, pp. 229-334.

______. 1923* Notes on the genus Erythemis. Univ. Mich. Mis. Zool. Misc. Pub. No. 11, pp. 3-1&.

Wilson, Charles B. 1920. Dragonflies and damselflies in relation to pondfish culture, with a list of those found near Fair- port, Iowa. Bull. U. S. Bur. Fish. 36*182-264. AUTOBIOGRAPHY

I, Neva Louise Currie, was "born near Loda, Illinois,

July 14, 1934* I received my elementary education at Meadow

Mound School, Wall Township, Ford County, Illinois, and my

secondary education at Paxton High School, Paxton, Illinois.

As an undergraduate I attended Millikin University in Decatur,

Illinois, and received the Bachelor of Arts degree from that

institution in 1956. I received the Master of Science degree

from The Ohio State University in 1958. During my graduate work

I have held in succession the positions of Graduate Assistant in

the Department of Zoology and Entomology, Research Fellow under

Dri Dwight M. Delong, and National Science^ Foundation Cooperative

Fellow.

100