Strepsiptera of Panama and Mesoamerica

Abstract

Abstract Strepsiptera are unique entomophagous parasitoids with free-living adult males and females that are neotenic and permanently endoparasitic in the host, except in the family Mengenillidae. The hosts include Thysanura, Blattodea, Mantodea, Orthoptera, Hemiptera, Diptera, and Hymenoptera. Of the 532 species described so far, 67 have been recorded from the Neotropics. The first instar larva is free-living and is the host-seeking stage of the parasitoid (Figs 27.2, 27.3). It usually parasitizes a host nymph (if the host is an exopterygote), or a host larva (if the host is an endopterygote). There have been reports that it also parasitizes host eggs (Linsley and MacSwain 19 57; Krombine 1967). When it enters the host it moults to an apodous second instar. The number of endoparasitic larval instars is not known for certain in most species except in Elenchus tenuicornis (Kirby), for which Kathirithamby et al. (1984) with correlated scanning and transmission electron microscopy showed that there are three. It is difficult to determine the number of endoparasitic larval instars because ecdysis does not follow apolysis; hence no exuviae (except that of the first instar) are found in the host. Nassonow (1910), Kirkpatrick (1937), Hassan (1939), Williams (1957), Baumert (1958, 1959), Kinzelbach (1967), Greathead (1968), Riek (1970), Kathirithamby (1978, 1982), and Waloff (19 81) estimated that there are one to seven instars. They based their estimates on such features as size increase owing to the lack of distinct morphological structures in the endoparasitic stages (Fig. 27.4).