Self-superparastism in solitary parasitoids implies that one or more eggs deposited in the same host by a female wasp will be lost as a consequence of competition among sibs. We used the braconid Aphidius nigripes and its aphid host Macrosiphum euphorbiae to test the hypotheses 1) that self-superparasitism varies with host instar/size, and 2) that it may be adaptive as a means of stimulating host feeding to obtain high quality progeny from immature/small hosts. The behavior of individual wasps was continuously monitored during three 5 min encounters, one with each one of three host sizes as defined by instars N1, N3 or Adult of the host. Hosts were immediately dissected to examine relationships between attack and oviposition frequencies. Female A. nigripes generated more attacks on Adult than N3 and especially N1 aphids. Despite attacks on adults being the least successful in terms of egg deposition, self-superparasitism occurred predominantly on these large hosts. Results support the hypothesis of a relationship between superparasitism and host development/size, but enhancing the quality of small immature hosts is not supported as an explanation. In a separate experiment, potential fitness consequences of self-superparasitism in adult hosts were examined by comparing several fitness indices among progenies from all three host instars receiving known numbers of successful attacks during a single encounter.
Species 1: Hymenoptera Braconidae Aphidius nigripes
Species 2: Homoptera Aphididae Macrosiphum euphorbiae (potato aphid)
Keywords: adaptative behavior, superparasitism
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