BEETLES. 



297 



Oedbe VII. — COLEOPTERA. 



The Beetles, or Coleoptera as they are termed by naturalists, briefly defined, are 

 six-legged insects, which have thick aud horny fore wings and chewing mouth-parts, 

 and which undergo complete metamorphosis. 



The most striking of these characters is the peculiar horn-like, opaque, usually 

 quite rigid fore wings, which, in the beetles, are termed elytra (singular elytron), from 

 the Greek elutron, meaning a sheath, a word used by Aristotle to designate the fore- 

 wings of beetles. These elytra give a general aspect to beetles which make them 

 easily recognizable as such, however much they may vary in other respects. As a 

 rule the elytra close together, meeting in a straight line along the posterior portion of 

 the back or dorsum of the insect, and shielding beneath them the delicate hind wings, 

 unless hind wings are absent, as is the case with a small number of beetles. The 

 elytra take no active part in the flight of Coleoptera, but generally are opened out- 

 ward at right angles to the body of the insect, remaining at rest in that position, 

 while the membranous hind wings perform the necessary strokes for locomotion. In 

 beetles that have rudimentary hind wings, and in those of which the hind wings are 

 absent, the elytron of one side usually is united firmly along the back to that of the 

 other side, to form a single shield, which protects the abdominal portions of the insect 

 beneath it. In one family, the Staphylinidse, or rove-beetles, and in some less com- 

 monly known beetles belonging to other families, the elytra are much too short or too 

 small to cover the whole abdomen, although the Staphylinidse manage to bring the 

 entire wings beneath the elytra by a complex system of folding. 



The name Coleoptera (from koleos, a sheath, and pteron, a wing) was first employed 

 for beetles by John Ray, an early English naturalist, in 1705, and has been generally 

 adopted by subsequent naturalists, although Fabricius, in 1775, teimed beetles Eleu- 

 therata, on account of their free maxillse, and Schluga, in 1767, used for 

 them the term Vaginata, from vagina, the Latin for sheath. 



The distinct division of the head, thorax, and abdomen, so clearly 

 discernible in most beetles, extends in less degree to their larvte. In 

 the larvae the head is usually quite distinct from the following segment. 

 The first three segments following the head, which correspond to the 

 thorax of the imago, are often quite different from the succeeding ab- 

 dominal segments of the larvae, but sometimes they closely resemble the 

 abdominal segments. The abdomen is usually more prolonged in pro- 

 portion to the thorax and head than it is in the imago, consequently 

 most beetle larvae have a vermiform appearance, which has given rise to 

 popular names, such as ' meal-worm ' for the larva of Tenebrio molitor, 

 and ' wire-worms ' for the larva of many Elateridae. The thicker and 

 more fleshy larvae of Coleoptera, such as are those often dug up about 

 roots, or split from their mines in wood, are in popular parlance ' grubs.' 



The larvEe of beetles mostly have six legs, or feet, near the anterior 

 end of their body, that is a pair of legs for each of the first three 

 segments behind the head — the thoracic segments. In the Curcu- 

 lionidae, and in some other beetles of which the larvae live within 

 their food, the latter are legless. Certain larvae have more or less developed 

 traces of anal legs, sometimes a product of the evaginated lateral portions of tM 



Fig. 344.— Larva 

 of Blaps pro- 

 ducta. 



