Fecundity and oviposition of Eucelatoria bryani, a gregarious parasitoid of Helicoverpa zea and Heliothis virescens

Abstract

We examined longevity, fecundity, and oviposition strategies of Eucelatoria bryani Sabrosky (Diptera: Tachinidae), a gregarious endoparasitoid of Helicoverpa zea (Boddie) and Heliothis virescens (F.) (Lepidoptera: Noctuidae). Longevity of adult female E. bryani was not related to body size. In contrast to longevity, larger E. bryani females had greater potential fecundity than smaller females, as determined by the number of embryonated eggs present in the common oviduct. However, female parasitoid size did not affect primary clutch size (number of eggs deposited in a host). Because embryos in eggs located in the ovisac were larger than those located elsewhere in the common oviduct, maximum primary clutch size may be physiologically limited by the number of fully mature eggs a female has available at one time. E. bryani females adjusted primary clutch size in response to host size, for both H. zea and H. virescens. This adjustment appears to be adaptive because females did not overexploit hosts by depositing more larvae than a host could support. Adult emergence was not related to host size. Although host weight positively influenced E. bryani progeny weight, increases in progeny size with host size were counterbalanced by increases in primary clutch size with host size.

Production of Dipteran Parasitoids

“…In the Cuban strain, two lines were successfully selected for puparial size (lowest and highest length), for eight generations, suggesting that such a selection could be used to improve the efficacy of this parasitoid as a biocontrol agent. Body size was found to be correlated with fitness and fecundity in L. diatraeae (King et al, 1976) and also in other tachinids like E. bryani (Reitz and Adler, 1995) and C. concinnata (Bourchier, 1991). In Cuba, attempts were made to maintain (and even improve) the quality of mass-reared L. diatraeae by modifying the composition of the G. mellonella diet, while taking into account production costs.…”

Interspecific competition between two parasitoids of Helicoverpa zea: Eucelatoria bryani and E. rubentis

“…E. rubentis females did not respond to this aspect of host quality, as they do to other aspects such as size or development stage (Reitz & Adler, 1995;Reitz, 1994) although the presence of E. bryani represents a significant cost to E. rubentis progeny. Given the relatively minor impact of E. rubentis on E. bryani, discrimination between unparasitized and heterospecifically parasitized hosts within the first 24 h following parasitism, is not necessary for E. bryani.…”

“…In contrast, the slower developing E. rubentis does not molt to the second instar until 24-36 h following oviposition (Reitz, 1994). Despite the brevity of oviposition bouts, females can adjust primary clutch size (number of eggs deposited in a host) in proportion to host size at the time of parasitization (Reitz & Adler, 1995). females might alter oviposition upon encountering hosts containing older parasitoid larvae, where their progeny would be less likely to survive.…”

Constraints on the Evolution of Host Choice by Phytophagous Insects

“…In general larger females have higher potential fecundity (Honek 1993, Preziozi et al 1996. The scaling relationship of longevity, however, appears much more variable than for fecundity; it may be positive (van den Assem et al 1989, McLain 1991, absent (Leather andBurnand 1987, Reitz andAdler 1995), or even negative (Carroll and Quiring 1993, Kraaijeveld and van der Wel 1994, Klingenberg and Spence 1997, Preziozi and Fairbairn 1997. Such interspecific variation in the scaling of potential fecundity and longevity suggests that the relationship between body size and opportunity per egg could vary widely across species (Fig.…”