VARIATION IN SELECTED LIFE-HISTORY PARAMETERS OF THE PARASITOID WASP,APHIDIUS-ERVI - INFLUENCE OF HOST DEVELOPMENTAL STAGE

We determined the age-specific fecundity and survival of the solitary parasitoid wasp, Aphidius ervi Haliday (Hymenoptera: Aphidiidae), unde r constant laboratory conditions. Wasps were reared in each of the fou r nymphal instars of apterous pea aphids, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae): L(1) (age 24 h), L(2) (48 h), L(3) (72 h), an d L(4) (120 h). Age-specific survival (l(x)) and fecundity (m(x)m) dif fered between parasitoids developing in different aphid instars. The w asps' life-time reproductive success, as indexed by the intrinsic rate of population increase (r(m)), varied non-linearly with adult biomass and host size at parasitization. A close agreement between larval gro wth rates in different host instars and adult reproductive performance suggests that, in A. ervi, fitness correlates may be significantly in fluenced by larval ontogeny and trade-offs in resource allocation.