External Structure

FIGURE 3.3. Structure of the typical pterygotan head. (A) Anterior; (B) lateral; (C) posterior; and (D) ventral (appendages removed). [From R. E. Snodgrass. Principles of Insect Morphology. Copyright 1935 by McGraw-Hill, Inc. Used with permission of McGraw-Hill Book Company.]

paired mandibles and maxillae occupy ventrolateral positions (Figure 3.3B). The mouth is situated behind the base of the labrum. The true ventral surface of the head capsule is the hypopharynx (Figure 3.3D), a membranous lobe that lies in the preoral cavity formed by the ventrally projecting mouthparts.

There are several grooves and pits on the head (Figure 3.3A-C), some of which, by virtue of their constancy of position within a particular insect group, constitute important taxonomic features. The grooves are almost all sulci. The postoccipital sulcus separates the maxillary and labial segments and internally forms a strong ridge to which are attached the muscles used in moving the head and from which the posterior arms of the tentorium arise (see following paragraph). The points of formation of these arms are seen externally as deep pits in the postoccipital groove, the posterior tentorial pits. The epicranial suture

FIGURE 3.4. (A) Prognathous; and (B) opisthognathous types of head structure. [A, from R. E. Snodgrass, Principles of Insect Morphology. Copyright 1935 by McGraw-Hill, Inc. Used with permission of McGraw-Hill Book Company. B, after R. F. Chapman, 1971, The Insects: Structure and Function. By permission of Elsevier North-Holland, Inc., and the author.]

FIGURE 3.4. (A) Prognathous; and (B) opisthognathous types of head structure. [A, from R. E. Snodgrass, Principles of Insect Morphology. Copyright 1935 by McGraw-Hill, Inc. Used with permission of McGraw-Hill Book Company. B, after R. F. Chapman, 1971, The Insects: Structure and Function. By permission of Elsevier North-Holland, Inc., and the author.]

is a line of weakness occupying a median dorsal position on the head. It is also known as the ecdysial line, for it is along this groove that the cuticle splits during ecdysis. In many insects the epicranial suture is in the shape of an inverted Y whose arms diverge above the median ocellus and pass ventrally over the anterior part of the head. The occipital sulcus, which is commonly found in orthopteroid insects, runs transversely across the posterior part of the cranium. Internally it forms a ridge that strengthens this region of the head. The subgenal sulcus is a lateral groove in the cranial wall running slightly above the mouthpart articulations. That part of the subgenal sulcus lying directly above the mandible is known as the pleurostomal sulcus; that part lying behind is the hypostomal sulcus, which is usually continuous with the postoccipital suture. In many insects the pleurostomal sulcus is continued across the front of the cranium (above the labrum), where it is known as the epistomal (frontoclypeal) sulcus. Within this sulcus lie the anterior tentorial pits, which indicate the internal origin of the anterior tentorial arms. The antennal and ocular sulci indicate internal cuticular ridges bracing the antennae and compound eyes, respectively. A subocular sulcus running dorsolaterally beneath the compound eye is often present.

FIGURE 3.5. Relationship of the tentorium to grooves and pits on the head. Most of the head capsule has been cutaway. [From R. E. Snodgrass. Principles of Insect Morphology. Copyright 1935 by McGraw-Hill, Inc. Used with permission of McGraw-Hill Book Company.]

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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