INTER- AND INTRASPECIFIC LARVAL COMPETITION INAPHIDIUS SMITHIANDPRAON PEQUODORUM(HYMENOPTERA: APHIDIIDAE)

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Abstract
Superparasitism and multiple parasitism of the pea aphid,Acyrthosiphon pisum(Harris), by the solitary hymenopterous parasitesAphidius smithiSharma & Subba Rao andPraon pequodorumViereck were studied in the laboratory. In intraspecific competition, an older larva usually eliminated a younger one; exceptions to this rule depended on the relative age difference and developmental stage of the competitors. In interspecific competition,P. pequodorumwas intrinsically superior toA. smithi, regardless of the latter's age. The stage of host parasitized and the number of competing larvae had no significant effect on the outcome of the contest.A. smithifemales discriminated against aphids previously parasitized by a conspecific female or byP. pequodorum, the degree of oviposition restraint increasing with the time between ovipositions.P. pequodorumfemales attacked aphids already parasitized byA. smithi, regardless of the age of theAphidiuslarva, but avoided oviposition when the aphid contained aPraonlarva or embryo. The rate of embryonic development is shown as a major factor in contest-type competition between first-stage larvae.