The fecundity, development and host relationships of Ceratobaeus spp. (Hymenoptera: Scelionidae), parasites of spider eggs

Abstract. 1. Ceratobaeus spp. enter the nest of their host spider and oviposit into eggs through the thin silk eggsac.
2. Temperatures below 15° C limit oviposition by slowing parasites down.
3. Males emerge prior to females and mate with their sibs. Sex ratios of 6.6–6.0:1 in favour of females were observed in the field and laboratory for two species.
4. Even though females can oviposit almost immediately after emergence their full complement of eggs (= 65) is not reached until several days later.
5. Superparasitism is low and appears to occur from subsequent accidental ovipositions. No marking of the external surface of hosts was observed.
6. Parasites overwinter as adults under bark. They do not feed as adults nor do they reabsorb their eggs, but rather oviposit as soon as host eggs become available in spring.
7. Successful oviposition occurs in later stages of host eggs reared at 15° C and 20° C than it does at 25°C. Different rates of development between host and parasite is proposed as an explanation for this phenomenon.
8. The species studied show varying degrees of specificity but each has a dominant host. Location of hosts involves cues from the habitat (bark), silk nests of spiders, and some factor associated with host eggs.