PROGENY ALLOCATION BY THE PARASITOID LESPESIA-ARCHIPPIVORA (DIPTERA, TACHINIDAE) IN LARVAE OF SPODOPTERA-EXIGUA (LEPIDOPTERA, NOCTUIDAE)

Field-collected Spodoptera exigua (Hubner) larvae always produce small brood sizes of the gregarious parasitoid Lespesia archippivora (Riley ) (1-2 progeny). To further investigate this finding we characterized life history attributes of the parasitoid's offspring in different hos t instars in the laboratory. Changes in offspring fitness and mortalit y and rate of successful parasitization can indicate opportunities for tachinids to influence fitness of their progeny. Effects of host inst ar and parasitoid brood size on parasitoid survival, development, size , and fecundity were investigated. Fecundity was indirectly assessed b y measuring parasitoid puparial weight; female puparial weight and egg load are positively correlated. L. archippivora is able to successful ly parasitize all investigated instars of S. exigua. The percentage of hosts yielding puparia was highest (95.1%) in 4th instars; it was onl y 65.5% in prepupal stages of the host. Lower parasitoid emergence rat es in younger host instars were caused by higher host survival or prem ature host mortality. Parasitoid puparial weight decreased with increa sing brood size but was not affected by host instar when equal brood s izes were compared. Parasitoid puparial weight with that of females fr om mixed sex broods of progeny. Progeny allocation of L. archippivora and fitness consequences associated with that allocation are independe nt of host size. We conclude that by consistently allotting small broo ds to hosts, L. archippivora adults may reduce strong competition betw een offspring and maximize successful parasitization, thereby resultin g in highly fit females.