Interactions Between Multiple Forms of Nuptial Feeding in the Wood Cricket Nemobius sylvestris (Bosc): Dual Spermatophores and Male Forewings

Abstract

Nuptial feeding is widespread in insects, with many species showing one form of feeding. In the wood cricket Nemobius sylvestris, the male may provide multiple forms of feeding during an encounter: two kinds of edible spermatophores (microspermatophore and macrospermatophore) and forewing secretions. We examined the roles and interactions of the spermatophores and forewing exposure in the mating sequence of this species. The small microspermatophore was not found to contain sperm, whereas the larger macrospermatophore contained sperm. In mating trials, the microspermatophore may be transferred to the female early in the trial. Transfer of the microspermatophore was not a necessary prerequisite to the subsequent transfer of one or more sperm‐filled macrospermatophores. Forewing exposure increased male mating success, as males with exposed forewings were more successful in transferring the macrospermatophore than males with experimentally covered forewings, both in terms of occurrence of successful transfer and the number of macrospermatophores transferred. Male mating success was very low when the male’s forewings were covered and when the male did not transfer a microspermatophore. The sperm‐filled macrospermatophore may have nutritional value, as females eventually consumed all transferred macrospermatophores, and males consumed all rejected macrospermatophores. Somewhat unexpectedly, this study casts doubt on the role of the forewings in nuptial feeding. Although males with exposed forewings were more successful in macrospermatophore transfer, females actually palpated these males’ forewings less. We posit the alternative hypothesis that the forewing secretions play a role in chemical communication to the female (e.g., signaling male quality), possibly instead of female nourishment.

Sexual Conflict Over Spermatophore Attachment in a Nuptially Feeding Cricket

“…This notion agrees with studies that show that food-limited females of nuptially feeding insects are more likely to copulate (e.g., Steele 1986a,b;Johnson et al 1999;Takakura 2004). The present study helps shed light on the function of female palpations of the males' wing secretions (Mays 1971;Bidochka & Snedden 1985;Choe 1995;Brown 1997;Fedorka & Mousseau 2002;Prokop & Maxwell 2008). Although the overall occurrence of female palpation was not significantly affected by female feeding regime, high-food females were more likely to palpate before microspermatophore transfer, while low-food females were more likely to palpate after macrospermatophore transfer.…”

“…2006), its premature removal is likely to reduce male fertilization success. Because trials with freely mobile males (normal and sham males) had longer macrospermatophore attachment durations, one can posit that the aggressive pursuit of the female by the male, observed in the present study and previously (Prokop & Maxwell 2008), might prevent the female from prematurely removing the macrospermatophore. This result adds support to previous suggestions that male pursuit and behavioral guarding may prolong spermatophore attachment in crickets (e.g., Loher & Rence 1978; Evans 1988; Hockham & Vahed 1997; Bateman & MacFadyen 1999; Bateman et al.…”

“…Ten mating trials were typically conducted simultaneously, with the experimenter observing the trials and recording the occurrence (to 1 min) of the following behaviors: female palpation of males’ forewings, production, transfer, attachment, and consumption of micro‐ and macrospermatophores. In contrast to gland‐feeding crickets (e.g., Bidochka & Snedden 1985; Brown 1997; Fedorka & Mousseau 2002), palpations by female N. sylvestris typically last for <1 min (Gabbutt 1954; Mays 1971; Prokop & Maxwell 2008). However, because low‐food females would mate opportunistically, longer palpations were expected.…”

“…In a typical mating encounter, the female may palpate the courting male’s right forewing. The male then transfers the spermless microspermatophore to the female, who may eat it (Gabbutt 1954; Prokop & Maxwell 2008). The male then transfers the larger sperm‐filled macrospermatophore, which attaches to the exterior of the female’s genital opening.…”

Cryptic Female Choice in Crickets and Relatives (Orthoptera: Ensifera)

“…In many cricket species, especially those in which pairs routinely engage in repeated mating, males direct a variety of post-copulatory behaviours towards the female (reviewed in Alexander andOtte 1967, Brown andGwynne 1997;Vahed 1998 see also Preston-Mafham 2000; Andrade and Mason 2000;Sadowski et al 2002;Zefa et al 2008;de Carvalho and Shaw 2010;Prokop and Maxwell 2008;, which could be interpreted either as a form of copulatory courtship (Eberhard 1991(Eberhard , 1996 or as mate "harassment" (Hall et al 2008). The former implies intersexual cooperation, while the latter implies intersexual conflict.…”