Eclosion

For exopterygotes adult emergence (eclosion) consists solely of escape from the cuticle of the previous instar. Many endopterygotes must, in addition, force their way out of the cocoon or cell in which pupation occurred and, in some species, to the surface of the substrate in which they have been buried. Some aquatic species that pupate under water have special devices to enable the adult to reach the water surface.

For adults of many species, emergence is triggered by environmental factors, especially temperature and photoperiod, or is entrained as a circadian rhythm (Myers, 2003) (see also Chapter 22, Sections 2.3 and 3.1.1). As aresult, emergence of populations of adults is highly synchronized, this being of particular importance in species whose adult life is short.

Eclosion is accomplished in a manner similar to larval-larval molts. A pharate adult swallows air to increase its body volume and, by contraction of abdominal muscles, forces hemolymph anteriorly. As the hemolymph pressure increases, the pupal cuticle splits along an ecdysial line on the thorax and/or head. In obtect pupae the pupal mouth is sealed over, but the adult swallows air that enters the pupal case via the tracheal system. Some adult spiracles remain in contact with those of the pupa, whereas others become separated so that a channel is open along which air can move into the pupal case.

Among more primitive endopterygotes an insect escapes from its cocoon or cell as a pharate adult using the mandibles of the decticous pupa to force an opening in the wall. Pharate adults of some species also have backwardly facing spines on the pupal cuticle, which enable them to wriggle out of the cell and through the substrate. Many primitive Lepidoptera and Diptera, whose pupae are adecticous, also escape as pharate adults, frequently making use of special spines (cocoon cutters) on the pupal cuticle. In higher Lepidoptera, adults may shed the pupal cuticle while still in the cocoon. In such species the cocoon may possess an "escape hatch" or part of it may be softened by special salivary secretions. Further, for those species that pupate in soil, the adult cuticle may become temporarily plasticized to facilitate tunneling to the surface. In muscomorph Diptera an eversible membranous sac on the head, the ptilinum, can be expanded by hemolymph pressure. This enables an adult to push off the tip of the puparium and tunnel to the surface of the substrate in which it has been buried. Adult Coleoptera, Hymenoptera, and Siphonaptera leave the pupal cuticle while in the cocoon or cell, then use their mandibles or cocoon cutters to cut their way out. In some species this is the sole function of the mandibles, which, like cocoon cutters, are shed after emergence.

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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