BEHAVIOR Reproductive Behavior of Thyanta pallidovirens (Heteroptera: Pentatomidae) QIAO WANG1 AND JOCELYN G. MILLAR2 Department of Entomology, University of California, Riverside, CA 92521 Ann. Entomol. Soc. Am. 90(3): 380-388 (1997) ABSTRACT Reproductive behavior of the stink bug Thyanta pallidovirens (Stal) was studied in the laboratory, including the determination of the sexual maturation period for both sexes, Downloaded from https://academic.oup.com/aesa/article/90/3/380/106886 by guest on 04 October 2021 the effects of the number of copulations on fecundity, and the function of prolonged copu- lation. Mean premating periods for males and females were 3.6 ± 0.5 and 4.1 ± 0.6 d, respectively. Preoviposition period averaged 6.6 ± 0.9 d. Females preferred sheltered, rough- textured oviposition sites. Paired adults mated =13 times on average during their lifespan under laboratory conditions. The mean duration of copulations involving virgin females was >17 h, significantly longer than that of subsequent copulations, which lasted between 6.9 and 8.3 h. Multiple matings significantly increased female fecundity. Virgin males donated =17% of their body mass to a virgin female during mating. Duration of mating may be regulated by space available in the spermatheca for ejaculatory material. There was strong evidence of male mate choice, with males terminating copulation with small females before sperm was trans- ferred. There was no indication of male mate-guarding behavior after copulation. Females almost always approached males from distances of >30 cm, suggesting that males attract females from a distance. Within 15 cm, males discern and approach females. Courtship be- haviors of males included antennation of female antennae and abdomens, stroking the abdo- mens with the hind legs, and periodic male abdominal vibrations. Possible functions of these behaviors are discussed. KEY WORDS Pentatomidae, Thyanta pallidovirens, reproductive behavior, nuptial gift THE NATIVE STINK bug Thyanta pallidovirens or more under optimal conditions (Schotzko and (Stal) is distributed through the far western states O'Keeffe 1990a). of the United States and into southern British Co- Aspects of the reproductive behavior of the Pen- lumbia (Schotzko and O'Keeffe 1990a). It was tatomidae have been studied by various authors identified as a major pest of nut crops in California (Borges et al. 1987; Kon et al. 1988; Todd 1989; in the mid-1980s. Damage to nuts caused by this McLain 1989, 1992; Drickamer and McPherson insect includes epicarp lesions, nut abortion and 1992). Reproductive behavior is often complex, kernel necrosis (Rice et al. 1985, 1988; Michailides with individuals of both sexes commonly mating et al. 1987). This insect is also a serious pest of many times (e.g. Kawada and Kitamura 1983, various legume and brassica crops (Schotzko and McLain et al. 1990), and large numbers of egg O'Keeffe 1990a, b). masses being oviposited over periods spanning sev- Adult bugs overwinter in orchard floor debris, eral months (e.g., Schotzko and O'Keeffe 1990a). under rocks, in soil cracks around the bases of host Mate location can involve chemical (Aldrich 1988) plants, or in other shielded places in and around and acoustic cues (Ota and Cold 1991), and there orchards (Rice et al. 1988). In California pistachio is evidence for some degree of mate choice by orchards, overwintering adults first appear in April both sexes (McLain 1980, 1989). or May, with adults of the 1st new generation In one of the few previous studies of T. palli- emerging in June or July. One or 2 additional over- dovirens reproductive behavior, Schotzko and lapping generations may develop during summer O'Keeffe (1990a) investigated ovipositional and and autumn. In the laboratory, this species will re- mating rhythms, and the variability in oviposition produce year-round under long-day conditions, S6s in response to different legume hosts. Because T. with the period from egg to adult averaging 25 pallidovirens is a serious pest of a variety of crops, d (vide infra), and adult longevity reaching 2 mo a better knowledge of its life history is needed. We report here the results of detailed investigations of the reproductive behavior in this species. In par- 'Current address: Department of Plant Science, Massey Uni- versity, Private Bag 11222, Palmerston North, New Zealand. ticular, our objectives were to observe and describe 2To whom correspondence should be addressed. T. pallidovirens reproductive behavior and behav- 0013-8746/97/0380-0388$02.00/0 © 1997 Entomological Society of America May 1997 WANG AND MILLAR: REPRODUCTIVE BEHAVIOR OF T. pallidovirens 381 ioral sequences; to measure parameters associated To determine the premating period for each sex with reproduction in this species, including sexual separately, 2 combinations of pairings were per- maturation periods, effects of single versus multi- formed: (1) newly emerged males were paired with ple matings on fecundity and egg hatch rates, the 10-d-old virgin females (n = 21), (2) newly duration and number of copulations, the number emerged females were paired with 10-d-old virgin of egg masses oviposited and the period between males (n = 19). sequential oviposition bouts; and to investigate the To determine preoviposition periods, 31 pairs of extent and effects of male investment in reproduc- freshly emerged insects were set up in individual tion in this species. containers. The time between emergence and the 1st copulation was recorded as the premating pe- riod, and that between emergence and 1st ovipo- Materials and Methods sition as the preoviposition period. Daily Mating Rhythms. Forty-one 10-d-old Downloaded from https://academic.oup.com/aesa/article/90/3/380/106886 by guest on 04 October 2021 Insects. In early August 1994, a laboratory col- pairs (1 pair per tube) were set up in 150-ml open- ony of T. pallidovirens was started from adults (31 ended plastic tubes with each end covered with males and 50 females) and nymphs (22 individuals) window screen, and observed hourly for 3 d, start- collected from alfalfa fields near Davis, CA, and ing 4 h into the photophase of the 1st observation from specimens obtained from a laboratory colony day. A piece of filter paper (6 by 2 cm), several (5 males, 7 females, and 30 nymphs) maintained sunflower seeds and half a green bean were placed at the Department of Entomology, University of in each half of the chamber. The number of cop- California, Davis. Insects were reared at 27 ± 1°C, ulating pairs was recorded hourly. 60 ± 10% RH, and a photoperiod of 16:8 (L:D) Effect of Single Versus Multiple Matings on h, with lighting provided by fluorescent lights. Fecundity. To determine whether the number of Food for nymphs and adults consisted of thor- matings influenced egg hatch rates and total num- oughly washed green beans from a supermarket, ber of eggs oviposited, bugs were set up in the organically grown sunflower seeds, and alfalfa cut- following 4 treatments, using 150-ml plastic tubes tings from an alfalfa plot in University of California as described above: (1) paired treatment. Thirty- Riverside Agricultural Operations. Green beans one pairs were kept in individual tubes for their and alfalfa were replaced every other day. All in- entire lifespans. The total number of matings per sects used for experiments were obtained from off- pair was determined by observing pairs thrice daily spring of the initial colony. (=1200 hours, 1700 hours, and just before lights The breeding colony was maintained in 2 wood- out each day). Because copulations are initiated en cages (76 by 43 by 43 cm), each containing 70- during the photophase, and because copulations 80 adults of both sexes. New adults were added to last for a number of hours (see Results), copula- the breeding cages every other day. Egg masses tions could be accurately tallied from these 3 ob- were collected from breeding cages every other servations. (2) Mated once treatment. Twenty- day, and kept in plastic petri dishes (10 by 1.5 cm), three pairs were placed in individual tubes and with 4 egg batches per dish. Upon hatching, males were removed immediately after the 1st nymphs were provided with fresh green beans and mating. (3) Mated 3 times treatment. Twenty-three sunflower seeds every other day. When nymphs females were allowed to mate 3 times with the reached the 2nd instar, they were transferred to same male at 5-d intervals in individual tubes, fol- cylindrical paper ice cream cartons (15 by 12.5 cm) lowed by permanent removal of the males. (4) Un- with window screen lids (^lOO nymphs per car- mated treatment. Twenty virgin females were ton). After the final molt, the adults were segre- maintained in tubes individually. gated by sex for use in experiments or added back For all treatments, egg masses were collected 3 to the breeding colony. times daily for the duration of the experiment and Sexual Maturation and Preoviposition Peri- incubated until hatching in individual petri dishes ods. Freshly emerged pairs (1 male, 1 female) of (10 by 1.5 cm diameter). The total number of eggs insects were set up in individual mating containers per mass and the number of eggs per mass that constructed from two 150-ml plastic tubes. One did not hatch were counted to determine hatch end of each tube was covered with window screen rates. and the open ends were fastened together with Male Investment in Reproduction. To examine transparent adhesive tape, and a piece of paper the relationship between the duration of copula- was used to separate the 2 halves of the chamber. tion and the amount of semen transferred by the A piece of filter paper (6 by 2 cm), several sun- male to the female during mating, body weights of flower seeds and half a green bean were placed in both sexes were measured before and after pro- each half of the chamber.