Effects of Host Size on Selected Fitness Components of Aphytis melinus and A. lingnanensis (Hymenoptera: Aphelinidae)

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Abstract
Two congeneric ectoparasitoids, Aphytis lingnanensis Compere and A. melinus DeBach, discriminated among different-sized hosts of California red scale, Aonidiella aurantii (Maskell). Both parasitoids laid male eggs on small scales and females on large scales, but the scale on which A. melinus began to lay female eggs was smaller than that laid upon by A. lingnanensis. No differences in immature parasitoid mortality based on host size were detected. Over a certain range of scale sizes, female parasitoid size directly correlated with host size, and at intermediate host size female pupal size attained its maximum in both species. Potential fecundity, as predicted by female size, differed between the species. Also, A. melinus generally matured fewer ovarian eggs less quickly than A. lingnanensis. Influence of survival, size, and fecundity on competitive interactions between these parasitoid species are discussed.