Effects of adult age and body size on egg maturation in the parasitoid Gronotoma micromorpha (Hymenoptera: Figitidae)

Abstract

The cynipoid wasp Gronotoma micromorpha (Perkins) (Hymenoptera: Figitidae) is a parasitoid of the leaf miner Liriomyza trifolii (Burgess) (Diptera: Agromyzidae). The effects of adult age and body size on egg maturation in G. micromorpha were determined. The results showed that its egg load (number of mature eggs per female) increased when offered honey, water, but not hosts for 3 or 6 days after adult emergence. However, there was no signifi cant difference in the egg loads of 3and 6-day-old wasps. These fi ndings and the results of previous studies on other cynipoid parasitoids suggest that when hosts are not available, females of parasitoid Cynipoidea enhance their reproductive capacity in anticipation of a future improvement in the availability of hosts by using carbohydrates and reserves stored during the larval stage. Moreover, large female wasps had higher egg loads throughout their lifetime. Given that rapid increases in the population density of L. trifolii are commonly reported in greenhouses, the demographic data of 0and 3-day-old G. micromorpha females fed honey, need to be compared in the future. The effects of body size on the fecundity and longevity of G. micromorpha wasps should also be determined. * Corresponding author; e-mail: y_abe@scs.kyushu-u.ac.jp INTRODUCTION Egg maturation in parasitoid wasps has been extensively investigated in order to clarify the life-history and reproductive strategies employed by these wasps (e.g., Rosenheim et al., 2000; Jervis et al., 2001, 2008). An ovigeny index, calculated by dividing the number of mature eggs upon emergence by potential lifetime fecundity, is widely used to assess a variety of reproductive traits of parasitoids (Jervis et al., 2001, 2008; Jervis & Ferns, 2004). From the viewpoint of reproduction, parasitoid wasps are classifi ed as pro-ovigenic species, in which most or all of the potential lifetime egg complement is mature upon emergence, or synovigenic species, in which egg maturation continues throughout the adult stage (Flanders, 1950). However, a continuum between pro-ovigenic and synovigenic has also been identifi ed in parasitoids, and strict pro-ovigeny (ovigeny index = 1) is rare (Jervis et al., 2001; Ellers & Jervis, 2004). Females emerging with a considerable number of mature eggs, combined with maturation of additional eggs throughout the lifetime of the female, are referred to as prosynovigenic parasitoids (Quicke, 1997). Host feeding and production of yolk-rich eggs are common in females of synovigenic species, which are typically Eur. J. Entomol. 118: 364–367, 2021 doi: 10.14411/eje.2021.038