Larval Crowding and Adult Nutrition Effects on Longevity and Fecundity of Female Trichogramma nubilale Ertle & Davis (Hymenoptera: Trichogrammatidae)

The influence of adult feeding of Trichogramma nubilale Ertle & Davis and larval competition within an egg of European corn borer, Ostrinia nubilalis Hübner, on progeny fecundity and longevity was tested. The number and sex of eggs laid were determined through direct observations. Hind tibial lengths were measured on females that were solitary or had shared a host egg with another wasp. Females were separated by size and provided either honey and excess hosts, honey and no hosts, no honey and hosts, or no honey and no hosts each day for their lifetimes. The number of mature eggs at eclosion was determined for several females by dissection of their ovarioles and counting their eggs. The mean hind tibial lengths of solitary females was 0.18 mm, whereas females that had shared a host egg with a male or female had hind tibial lengths of 0.14-0.16 mm. Solitary females had 2.3 times more eggs and lived 1.2 times longer than females that had shared the host with a male or female. Honey increased fecundity by factors of 1.6 and 1.9 and longevity by 5.4 and 4.8 d for solitary females and those that had shared a host egg, respectively. Females that are not fed lay the same number of eggs as estimated from dissected females at eclosion, suggesting that females mature additional eggs only if they are fed as adults. Some implications for inundative releases of T. nubilale against European corn borer in the field are discussed.