Life History and Habits

The principal hosts of Strepsiptera are Auchenorrhyncha, and Sphecoidea, Vespoidea, and Apoidea within the Hymenoptera. Other hosts include Thysanura, Orthoptera, Dicty-optera, Heteroptera, Diptera, and other aculeate Hymenoptera. Members of a given strep-sipteran family usually are parasitoids of only one or a very few major insect groups; for example, Mengenillidae are known only from Thysanura. However, at the generic and specific levels the degree ofhost specificity is varied. It is generally high when a hymenopteran is the host, lower if the host is ahomopteran. Both sexes ofthe host are used, and both sexes of the parasitoid may occur on the same host, in varied numbers. Curiously, in Myrmecolacidae male and female larvae use hosts from different taxa (see below). The location at which the parasitoid protrudes from the host varies but is generally specific for a particular genus.

After emergence, males, which survive for only a few hours, search actively for a virgin female. She assists by releasing an attractant pheromone. Except in Mengenillidae, copulation occurs on the host. In some species it appears that parthenogenesis is probable. The embryos develop within the female's body, which presumably receives nourishment by direct absorption through the very thin puparial cuticle. On hatching, the triungulins (usually several thousand are produced by a female) escape via the brood passage. They usually remain on the host in large numbers until an opportunity presents itself for entering a new (immature) host. The precise details of this process have rarely been observed, but it is assumed to occur in the nest in species that are parasitoids of Hymenoptera or on plants in species using other groups. The triungulins are active and, in many species, capable of jumping for distances of 2 or 3 cm using the caudal setae. They normally enter the host via the abdominal cuticle, though entry via the host's tarsi has recently been recorded (Kathirithamby, 2001). Entry is gained through a combination of enzymatic and physical activity. Fluid is secreted from the mouth and appears to partially dissolve the host's cuticle. Within the host a larva soon molts to the second stage, a more grublike form. In Elenchus tenuicornis third and fourth instars follow, though these do not shed the previous instar cuticles, which remain as a sheath around the larva. The final-instar larva moves to the host's integument; in Mengenillidae it leaves the host to pupate under stones, etc., but in other families (suborder Stylopidia) the larva only extrudes its anterior end outside the host before pupating (Figure 10.21B). Again, the last larval cuticle is not shed but becomes tanned and remains as a puparium within which metamorphosis occurs. Extrusion usually coincides with the final larval or pupal stage of the host. The presence of the parasitoid is not without effect on the host, which is said to be stylopized. Most noticeable are changes in the structure of the external genitalia and other external sexual characters, and atrophy of the gonads and other internal structures. Whether these changes are directly caused by the parasitoid or are merely the result of inadequate nutrition, is not known. Female hosts with parasitoids are not fertile, but males may be.

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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