FECUNDITY, LONGEVITY, AND SEX RATIO OF APHIDIUS NIGRIPES (HYMENOPTERA: APHIDIIDAE) PARASITIZING DIFFERENT STAGES OF ITS HOST, MACROSIPHUM EUPHORBIAE (HOMOPTERA: APHIDIDAE)

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Abstract
The longevity and age specific fecundity, as well as the sex ratio of the progeny, were obtained for Aphidius nigripes Ashmead females given access to the five developmental stages of the potato aphid, Macrosiphum euphorbiae (Thomas). Neither female longevity nor fecundity, as measured by the total number of aphids parasitized, were significantly different for the various host stages. The percentage of females in the progeny decreased as the female parasite aged, and the overall sex ratio of progeny was significantly affected by the host stage attacked although no direct relationship with host size was evident. However in a separate experiment where parasitism was controlled (females not permitted to attack more than 10 hosts per day), the host stage (size) significantly affected the sex ratio of progeny, with more females emerging from larger than smaller hosts.These data indicate that all developmental stages of M. euphorbiae, when presented separately, are suitable to A. nigripes.
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