Egg Maturation and Daily Progeny Production in the Parasitoid, Gronotoma micromorpha (Hymenoptera: Figitidae: Eucoilinae).

Abstract

An ovigeny index, which is the initial egg load divided by the potential lifetime fecundity, was developed for the parasitoid, Gronotoma micromorpha (Perkins), on the host Liriomyza trifolii (Burgess) (Diptera: Agromyzidae). The value obtained for the index was estimated to be 0.54, based on the initial egg load (mean ± SD: 41.0 ± 13.5) observed in the present study and the lifetime fecundity (75.6 ± 32.6) estimated in a previous study. Gronotoma micromorpha was previously regarded as being strictly pro-ovigenic based on daily progeny production data; however, the findings of the present study showed that this parasitoid is prosynovigenic. A 3-d cycle in daily progeny production was previously reported to occur during the lifetime of adult females (6.6 d) in this species. The present study showed that the initial egg load is nearly equal to the total number of eggs deposited in 3 d following adult emergence. Therefore, it is considered that the mature eggs stored during the pupal stage are deposited during the first 3 d after adult emergence and that egg maturation in the adult stage starts on day 1 and requires 3 d to complete in G. micromorpha. To clarify the relationship between the daily progeny production and the initial egg load, a reproductive cycle consisting of maturation, deposition, and depletion of eggs is proposed. In G. micromorpha, the reproductive cycle is considered to occur twice during the female lifetime. Furthermore, it is proposed that other prosynovigenic parasitoid species have a similar reproductive cycle.