Gas Exchange in Endoparasitic Insects

It is probably not surprising that endoparasitic insects, as they too are surrounded by fluid, show many parallels with aquatic insects in the way that they obtain oxygen. Most endoparasites satisfy a proportion of their requirements by cutaneous diffusion. In some first-instar larvae of Hymenoptera and Diptera the tracheal system may be liquid-filled, but generally it is gas-filled with closed spiracles and includes a rich network of branches immediately beneath the integument. Many endoparasitic forms, especially larval Braconidae, Chalcididae, and Ichneumonidae (Hymenoptera), and some Diptera, possess 'tails' filled with hemolymph or can evaginate the wall of the hindgut through the anus. It has been suggested that these structures may facilitate gas exchange, though the evidence on which this suggestion is based is generally not strong.

Endoparasites with greater oxygen requirements usually are in direct contact with atmospheric air either via the integument of the host or via the host's tracheal system. In larvae of many Chalcidoidea, for example, only the posterior spiracles are functional, and these open into an air cavity formed at the base of the egg pedicel that penetrates the host's integument (Figure 15.9A). Many larval Tachinidae (Diptera) become enclosed in a

FIGURE 15.9. Respiratory systems of endoparasites. (A) Larva of Blastothrix (Hymenoptera) attached posteriorly to remains of egg, thereby maintaining contact with the atmosphere via the egg pedicel; and (B) larva of Thrixion (Diptera) surrounded by the respiratory funnel formed by ingrowth of the host's integument. [From A. D. Imms, 1937, Recent Advances in Entomology, 2nd ed. By permission of Churchill-Livingstone, Publishers.)

FIGURE 15.9. Respiratory systems of endoparasites. (A) Larva of Blastothrix (Hymenoptera) attached posteriorly to remains of egg, thereby maintaining contact with the atmosphere via the egg pedicel; and (B) larva of Thrixion (Diptera) surrounded by the respiratory funnel formed by ingrowth of the host's integument. [From A. D. Imms, 1937, Recent Advances in Entomology, 2nd ed. By permission of Churchill-Livingstone, Publishers.)

respiratory funnel produced by the host in an attempt to encapsulate the parasite (Figure 15.9B). The funnel is produced by inward growth of the host's integument or tracheal wall. Within it, the parasite attaches itself by means of mouth hooks while retaining contact with atmospheric air via the entrance of the funnel.

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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