The Extant Hexapoda

The Hexapoda (usually given the rank of superclass) contains all six-legged arthropods. Traditionally, the closest relatives of hexapods have been considered to be the myriapods (centipedes, millipedes, and their allies). However, as shown in Box 7.2, molecular sequence and developmental data plus some morphology (especially of the compound eye and nervous system) suggest a more recent shared ancestry for hexapods and crustaceans than for hexapods and myriapods.

Diagnostic features of the Hexapoda include the possession of a unique tagmosis (section 2.2), which is the specialization of successive body segments that more or less unite to form sections or tagmata, namely the head, thorax, and abdomen. The head is composed of a pregnathal region (usually considered to be three segments) and three gnathal segments bearing mandibles, maxillae, and labium, respectively; the eyes are variously developed, and may be lacking. The thorax comprises three segments, each of which bears one pair of legs, and each thoracic leg has a maximum of six segments in extant forms, but was primitively 11-segmented with up to five exites (outer appendages of the leg), a coxal endite (an inner appendage of the leg), and two terminal claws. The abdomen origin ally had 11 segments plus a telson or some homologous structure; if abdominal limbs are present, they are smaller and weaker than those on the thorax, and primitively were present on all except the tenth segment.

The earliest branches in the hexapod phylogeny undoubtedly involve organisms whose ancestors were terrestrial (non-aquatic) and wingless. However, any combined grouping of these taxa is not monophyletic, being based on evident symplesiomorphies (e.g. lack of wings, or the occurrence of molts after sexual maturity) or otherwise doubtfully derived character states. So a grouping of apterygote (primitively wingless) hexapods is a grade of organization, not a clade. Included orders are Protura, Collembola, Diplura, Archaeognatha, and Zygentoma. The Insecta proper comprise Archaeog-natha, Zygentoma, and the huge radiation of Pterygota (the primarily winged hexapods).

Relationships are uncertain among the component taxa that branch from nodes near the base of the phylo-genetic tree of the Hexapoda, although the cladograms

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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