Variation in selected life‐history parameters of the parasitoid wasp, Aphidius ervi: influence of host developmental stage

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Abstract
We determined the age‐specific fecundity and survival of the solitary parasitoid wasp, Aphidius ervi Haliday (Hymenoptera: Aphidiidae), under constant laboratory conditions. Wasps were reared in each of the four nymphal instars of apterous pea aphids, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae): (age 24 h), L2 (48 h), L3 (72 h), and L4 (120 h). Age‐specific survival (lx) and fecundity (mx) differed between parasitoids developing in different aphid instars. The wasps' life‐time reproductive success, as indexed by the intrinsic rate of population increase (rm), varied non‐linearly with adult biomass and host size at parasitization. A close agreement between larval growth rates in different host instars and adult reproductive performance suggests that, in A. ervi, fitness correlates may be significantly influenced by larval ontogeny and trade‐offs in resource allocation.