Foregut

The foregut, formed during embryogenesis by invagination of the integument, is lined with cuticle (the intima) that is shed at each molt. Surrounding the intima, which may be folded to enable the gut to stretch when filled, is a thin epidermis, small bundles of longitudinal muscle, a thick layer of circular muscle, and a layer of connective tissue through which run nerves and tracheae (Figure 16.2). The foregut is generally differentiated into pharynx, esophagus, crop, and proventriculus. Attached to the pharyngeal intima are dilator muscles. These are especially well developed in sucking insects and form the pharyngeal pump (Chapter 3, Section 3.2.2). The esophagus is usually narrow but posteriorly may be dilated to form the crop where food is stored. In Diptera and Lepidoptera, however, the crop is actually a diverticulum off the esophagus. During storage the food may undergo some digestion in insects whose saliva contains enzymes or that regurgitate digestive fluid from the midgut. In some species the intima of the crop forms spines or ridges that probably aid in breaking up solid food into smaller particles and mixing in the digestive fluid (Figure 16.2A). The hindmost region of the foregut is the proventriculus, which may serve as a valve regulating the rate at which food enters the midgut, as a filter separating liquid and solid components, or as a grinder to further break up solid material. Its structure is, accordingly, quite varied. In species where it acts as a valve the intima of the proventriculus may form longitudinal folds and the circular muscle layer is thickened to form a sphincter. When a filter, the proventriculus contains spines that hold back the solid material, permitting only liquids to move posteriorly. Where the proventriculus acts as a gizzard, grinding up food, the intima is formed into strong, radially arranged teeth, and a thick layer of circular muscle covers the entire structure (Figure 16.2B).

Posteriorly the foregut is invaginated slightly into the midgut to form the esophageal (= stomodeal) invagination (Figure 16.3). Its function is to ensure that food enters the

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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