AGGREGATION, COURTSHIP, AND BEHAVIORAL INTERACTIONS IN EUROPEAN EARWIGS, FORFICULA AURICULARIA L. (DERMAPTERA: FORFICULIDAE) by Karen Ann Walker Dissertation submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY IN ENTOMOLOGY APPROVED: Kha pipet! Richard D. Fell, Chair Jeffrey R. Bloomquist _ ““FtiomasA. Jenssen A, ph Donald E. Mullins W. Wayne Surles April 11, 1997 Blacksburg, Virginia Keywords: European earwig, aggregation, courtship, social behavior ct LD 5655 V8S6 99 F W354 AGGREGATION, COURTSHIP, AND BEHAVIORAL INTERACTIONS IN EUROPEAN EARWIGS, FORFICULA AURICULARIA L. (DERMAPTERA: FORFICULIDAE) by Karen Ann Walker Richard D. Fell, Chairman (ABSTRACT) Due to its relatively cool, humid summers, southwestern Virginia provides an ideal climate for European earwigs, Forficula aunculana.. |In 1990 - 1992, nymphs were captured in wooden groove-board traps beginning in late May , adults were captured beginning in mid-June, and disappeared from sampling sites by September or October. Sex ratios were significantly female-biased most of the season, becoming more marked by the fall. The pest status of F. auncularia is exacerbated by its gregarious nature. Gas chromatography-mass spectroscopy and accompanying behavioral bioassays showed that aggregation occurred as a result of a pheromone located on the male cuticle, which is probably a minor component of the hydrocarbon profile. Approximately 88% of the detected volatiles on the cuticle were identified. as a series of normal and branched alkanes. Fatty acids and hydrocarbons were also identified in nymphal and adult legs, but these extracts were not attractive. Frass, which also contained fatty acids and hydrocarbons, was attractive, but likely acquired its attractancy through the earwigs’ proclivity for consuming carcasses and exuviae. The defensive quinones produced by F aunculana repel conspecifics. A study of the behavioral repertoire of F. aunculana showed that, contrary to previous reports, only nymphs are nocturnal. Many differences in behavior were due to gender, age, and partner age. (e.g., females spent more time feeding than did males, adults fed more when paired with nymphs than when paired with adults). Social behaviors (communal feeding, aggression, contact , and dorsal palpation) comprised <10% of the insect’s behavioral repertoire. Since dorsal palpation, a previously undescribed behavior and a form of allogrooming, occurred more frequently during reproductive periods, it may have a sexual significance. Dorsal palpation also may augment the distribution of defensive quinones on the cuticle of F. auriculana. An analysis of nymphal group dynamics demonstrated that as group size increased, nymphs spent significantly less time feeding alone and grooming, but more time resting. Antennal contact rates between group members increased significantly with group size. Detailed observations of the courtship and mating of F. auricularia revealed a complex of sexual behaviors for both males and females. Receptive females were behaviorally active during courtship. The significance of the male cerci was demonstrated by their use in early courtship with displays, and later use as a tactile stimulus for the female; and study of males from which the cerci had been removed, which showed no mating by amputated males. Male forcep length was bimodailly distributed and positively allometric, while female forcep length was normally distributed. Males with longer forceps did not have a mating advantage. Further research is needed to identify the chemical composition of the aggregation pheromone, and to quantify any advantages of body and forcep size on mating success. ACKNOWLEDGMENTS | extend thanks to my committee, especially my adviser, Dr. Richard Fell, for their support and encouragement. | also wish to thank several people who lent me assistance throughout the course of the research: Tappey Jones and Lewis Pannell at the National Institutes of Health in Bethesda, Maryland, for help with the gas chromatography-mass spectroscopy; Larry Rockwood at George Mason University in Fairfax, Virginia, for allowing me the use of his analytical balance; Keith Tignor, for assistance with some of the earwig collection; and Eric Day, for information about citizen calls to the Virginia Cooperative Extension Service in Blacksburg. June Mullins drew the diagram of mating behavior. Deb Davidson provided encouragement and support. | particularly thank Paul Andrews, who helped with typing, computer graphics, videotaping, attitude adjustment, and support through the fruition of this dissertation, a long mission. My son, William, helped keep everything lively, and the births and infancies of my daughter Alison and son Nicholas compounded the fun of analysis and writing. The following are some of the many who kindly allowed me to collect earwigs on their property, or collected earwigs for me: Dr. Richard Fell, Dr. Michael Kosztarab, Dr. Donald Mullins, Dr. John Weidhaas, Belinda and Dave Carroll, Harlan Hendricks, Noma Wilkinson, Glenn Sadler, Betsy Bernard, Evelyn Hogge, Jackie Hoell, Miriam Matz, Lana Matzuk, Peggy Hubble, Jenny Moore, Lucy Ryan, Martha Blankenship, and Dick McDonald. CONTENTS ABSTRACT . 2. ACKNOWLEDGMENTS Co . LISTOF FIGURES... ... rn || LISTOF TABLES. ..... Coe INTRODUCTION... Ce . 2 1 LITERATURE REVIEW . 3 Taxonomy, Morphology andd Geographical Distribution . 3 Life Cycle . Cee . 5 Ecology Lo . 8 Economic Importance . .11 Aggregation Behavior . 14 Chemical Defenses .17 Social Behavior and Organization . .19 Aggression. , . 19 Forceps Function ._. 20 Courtship and Mating . .23 Parental Care . .23 CHAPTER 1: LIFE HISTORY, POPULATION CHARACTERISTICS AND SEX RATIO. ©. 2... we 0 Introduction... Ce ee 80 Materials and Methods. Ce BD Earwig Collection . 32 WeatherData. 2... ee 8B AdultDevelopment . .. a 8D Pest Status. ... .40 Results. .. Ce 40 Population Dynamics Ce . 40 Adult Development... , . 50 Qualitative Observations on Pest Status Coe ee ee 50 Discussion. .. ee . 93 Population Characteristics . Coe 88 Sex Ratios. 2... Pest Status. ... .59 CHAPTER 2: AGGREGATION BEHAVIOR . 61 Introduction oo, . 61 Materials and Methods. 62 Laboratory Conditions. 62 Preliminary Aggregation Experiments . 66 Natural Extracts Lo. .t1 Chemical Analyses .12 Aggregation Bioassays 13 Statistics ; . 78 Results. .. .19 Preliminary Aggregation Experiments . .19 Chemical Analyses of Extracts. 81 Behavioral Response to Extracts . 91 Discussion . 95 CHAPTER 3: BEHAVIORAL REPERTOIRE AND SOCIAL INTERACTIONS. .104 Introduction .104 Materials and Methods. Lo. 107 Videotaping of Earwig Dyads and Groups. 107 Videotape Review ee 115 Statistics 115 Results... 117 Activity Budgets 117 Effect of Vanables on Behavior 123 Correlations of Individual Behaviors 133 Group Behavior 133 Discussion. .136 Activity Budgets .136 Behaviors and Social Interactions . 139 Group Dynamics 143 CHAPTER 4: COURTSHIP AND MATING BEHAVIOR .146 Introduction 146 Materials and Methods. , .148 Courtship Behavioral Repertoire .148 Male-male Interactions. .150 Ablated males . .150 Body Measurements .151 Results. 152 Courtship Beha vioral Repertoire .152 Male-male Interactions. .163 Dorsal Palpation .164 Ablated Males . .165 Body Measurements 166 Discussion . 172 vi CONCLUSIONS . we e182 LITERATURE CITED. 189 VITA 2. ww, . 202 Vil LIST OF FIGURES CHAPTER 1: LIFE HISTORY, POPULATION CHARACTERISTICS AND SEX RATIO Figure 1.1. «41 Mean number of F. auricularia nymphs collected at Sites 1 and 2i in Blacksburg, Virginia, in 1990 and 1991. Figure 1.2. Lo. toe le 48 Monthly mean minimum and r maximum n temperatures recorded at a meteorological station in Blacksburg, Virginia during 1990 and 1991. High (h), low (I), average from 1952-1992 (ave). Figure 1.3. , . 44 Total monthly and average (from 1952-1992) precipitation recorded at a meteorological station in Blacksburg, Virginia during 1990 and 1991. Figure 1.4. , . 46 Age and sexual distribution of F. auricularia at Sites 1, 2 and 3 in Blacksburg, Virginia in 1990. (N=1,731; N=683; N=416, v 2295 7, df=1, P<0.05; N=741, X *=15.5, df=1, P<0.05; N=569, X *=18.6, df=1, P<0.05; N=266, X *=6.6, df=1, P<0.05; N=573, y °=16.4, df=1, P<0.05; N=549, y 7=42.3, df=1, P<0.05; N=207, 7 *=16.8, df=1, P<0.05, N=16 from late May through mid-October, respectively). Figure 1.5. 47 Age and sexual distribution of F. auricularia at Sites 1 5 i in Blacksburg, Virginia iin 1991. (N=690, XY *=10.7, df=1, P<0.05; N=534:N=889, XY *=8.7, df=1, P<0.05; N=298, yv *=18.7, df=1, P<0.05; N=127; N=202, X *=24.5, df=1, P<0.05; N=144, x °=13.4, df=1, P<0.05, from late May through mid-September, respectively). Figure 1.6. , . 48 Age and sexual distribution of F. auricularia at Sites 6 (NE=242, r 2=6, 3, df=1, P<0.05) and 7 (N=157) in Christiansburg, Virginia in mid-June 1990, and Sites 8 (N=66), 9 (N=249), 10 (N=246, v *=5.3, df=1, P<0.05), and 11 (N=242) in Blacksburg, Virginia in July 1990. CHAPTER 2: AGGREGATION BEHAVIOR Figure 2.1. , . 82 Distribution of F. auricularia i in two. adjacent traps (N==6 replicates) i in Blacksburg, Virginia, in 1990. One trap had been previously exposed to earwigs (old), and one had not (new). Significant a values (df=1) are given. Except for Day 6, P <0.001 for all sampling days. Figure 2.2. Lo. , 84 Structural formulae for selected chemical components of F. auricularia frass, defensive secretions, or cuticle. Figure 2.3. oo, . , 85 Gas chromatogram of methylene chloride washes of female F. auricularia cuticle, with identified peaks. viii Figure 2.4. 86 Gas chromatogram of methylene chloride washes of male F. auricularia cuticle. Figure 2.5. 89 Gas chromatogram of methylene chloride washes of F auricularia frass, with identified peaks. Figure 2.6. 90 Gas chromatogram of methylene chloride washes of F. auricularia nymph legs, with identified peaks. CHAPTER 3: BEHAVIORAL REPERTOIRE AND SOCIAL INTERACTIONS Figure 3.1 . .118 Activity budget for male F. auricularia (N= 64), with percent time allocated to fi ive behaviors.