The biology of Physcus seminotus Silv. and P. subflavus Annecke & Insley (Aphelinidae), parasites of the sugar-cane scale insect Aulacaspis tegalensis (Zhnt.) (Diaspididae)

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Abstract
Physcus seminotus Silv. (properly P. sp. nr. seminotus Silv.) and P. subflavus Annecke & Insley (Aphelinidae) are parasites of the sugar-cane scale insect Aulacaspis tegalensis (Zhnt.) (Diaspididae) in East Africa and they have been purposely introduced into Mauritius where A. tegalensis is an important pest. P. seminotus has brachypterous, flightless females and P. subflavus winged females but their biology is essentially similar. The parasites are arrhenotokous and fertilised and unfertilised eggs are deposited in different sites concomitant with development of female and male larvae on different primary hosts. Female larvae develop endoparasitically in A. tegalensis from fertilised eggs deposited in the host's body cavity. Male larvae develop ectoparasitically on immature Hymenoptera in A. tegalensis from unfertilised eggs deposited in the air-filled cavity of the latter's integumentary remnant. The males of the two Physcus spp. are therefore hyperparasitic and they frequently develop on the immature stages, both male and female, of their own kind (autoparasitism). Unfertilised eggs are laid by virgin females and also by mated females, the latter being able to deposit fertilised and unfertilised eggs at will, depending on the egg site encountered. Sexual dimorphism occurs at all stages, including the deposited egg. The preovipositional adult is the preferred stage of A. tegalensis for deposition of fertilised eggs and development of females is most rapid in such hosts. Development in young hosts is arrested until the hosts have grown to virtually their full size. The host of a male is apparently a matter of chance in so far as evelopment will occur on larval and pupal Hymenoptera of various species found in the empty, inflated, brittle integument of parasitised A. tegalensis. Only one individual, whether male or female, develops per host. Oviposition behaviour of mated females is such that superparasitism is largely avoided but it is liable to occur frequently when virgin females oviposit. Adult females will feed on the body fluids of A. tegalensis that are released by insertion of the ovipositor and also on sugary fluids. They live a month or more, ovipositing continually at a gradually decreasing rate, and laying usually 50–100 eggs.