Saliva and food ingestion

Salivary secretions dilute the ingested food and adjust its pH and ionic content. The saliva often contains digestive enzymes and, in blood-feeding insects, anticoagulants and thinning agents are present. In insects with extra-intestinal digestion, such as predatory Hemiptera, digestive enzymes are exported into the food and the resulting liquid is ingested. Most Hemiptera produce an alkaline watery saliva that is a vehicle for enzymes (either digestive or lytic), and a proteinaceous solidifying saliva that either forms a complete sheath around the mouthparts (stylets) as they pierce and penetrate the food or just a securing flange at the point of entry (section 11.2.4, Fig. 11.4c). Stylet-sheath feeding is characteristic of phloem- and xylem-feeding Hemiptera, such as aphids, scale insects (coccoids), and spittle bugs, which leave visible tracks formed of exuded solidifying saliva in the plant tissue on which they have fed. The sheath may function to guide the stylets, prevent loss of fluid from damaged cells, and/or absorb necrosis-inducing compounds to reduce defensive reaction by the plant. By comparison, a macerate-and-flush strategy is typical of Heteroptera,

Fig. 3.15 Longitudinal section through the anterior body of a caterpillar of the small white, small cabbage white, or cabbage white butterfly, Pieris rapae (Lepidoptera: Pieridae). Note the thickened epidermal layer lining the midgut.

such as mirids and coreids. These insects disrupt the tissues of plants or other insects by thrusting of the stylets and/or by addition of salivary enzymes. The macerated and/or partly digested food is "flushed out" with saliva and ingested by sucking.

In fluid-feeding insects, prominent dilator muscles attach to the walls of the pharynx and / or the preoral cavity (cibarium) to form a pump (Fig. 3.14b), although most other insects have some sort of pharyngeal pump (Fig. 3.14a) for drinking and air intake to facilitate cuticle expansion during a molt.

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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