There is a baffling array of anatomical and biological diversity within the order. However, some basic anatomical features are shared by most beetles, and these are outlined in the diagram below:
Beetles are characterised by their hardened, shield-like forewings (which also gave the class its name: coleo = shield, and ptera = wing). These forewings, called elytra, are not used in flying, but cover the rear part of the body and protect the hind wings when not in use. The hind wings are longer than the elytra when extended for flight, and have complex pleating which allows them to be folded beneath the elytra when at rest.
The bodies of beetles are divided into three sections: the head, the thorax, and the abdomen. The thorax is further divided into an anterior prothorax, and posterior pterothorax. The morphology and size of the antenna can vary greatly (longhorn beetles (Cerambycidae) have antennae which are often as long as or longer than the beetle's body), but they generally consist of 11 or fewer segments. As with all hexapods beetles have six legs, which often bear variously shaped claws and adhesive structures. Sometimes they are modified for swimming, jumping, or digging in soil or wood.
Beetles range in size from the minute North American Nanosella fungi feather-winged beetles (Ptiliidae), adults of which are as small as 0.3 mm long, to the giant Titanus giganteus long-horned beetles (Cerambycidae) of South America, which can be 20 cm in length.
Beetle larvae vary in body shape and leg structure. Some are apodous (lacking any thoracic legs), whilst legged larvae may be campodeiform (elongate with long legs), eruciform (grub-like with short legs), or scarabaeiform (grub-like with long legs). The larvae generally have a hardened head capsule with opposable mandibles. Pupation usually occurs in a specially constructed cell or chamber, although some species spin a cocoon from silk, and some remain exposed.
Author: Phil Jardine
Last updated: 21st November 2005
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