ENTOMOLOGY IX OUTLINE COLEOPTERA. 97 



Beetles are characterized by the possession of a pair of horny wing- 

 covers, called elytra, which meet in a straight line down the back, and 

 beneath which is a single pair of membranous wings. They possess 

 biting mouth parts, and the metamorphosis is complete. The earwigs 

 are the only insects that might be mistaken for beetles, but as they pos- 

 sess a pair of pincers-like appendages at the end of the body, they may 

 be readily distinguished from them. 



The name Coleoptera is derived from the Greek coleos, a sheath, and 

 pteron, a wing. The name refers to the sheath-like structure of the 

 elytra, which were formerly believed to be modified wings, but which are 

 now known to be homologous to the plates, or paraptera, which exist 

 at the bases of the wings of the lower orders of insects. The true wings 

 are membranous, and are efficient organs of flight in most species. 

 When at rest they are folded beneath the elytra. In those species 

 which have no true wings, the elytra serve only as a protection to the 

 soft abdomen. The mouth parts are evenly proportioned, no part being 

 over-developed at the expense of others, as in the Lepidoptera or 

 Hymenoptera. The upper lip, or labrum, is usually distinct; the upper 

 pair of jaws, or mandibles, are strong and fitted for seizing or gnawing; 

 the lower jaws, or maxillae, are composed of several distinct pieces, and 

 bear prominent palpi; the lower lip, or labium, is also complicated in 

 structure, and bears prominent palpi. The antennae of beetles are 

 extremely varied in form, being serrate, clavate, momliform, or irregular, 

 as the case may be. The tarsi, or feet, have from three to five joints, 

 the last joint usually terminating in a pair of claws. 



Since Coleoptera possess no easy means of identification, entomol- 

 ogists have had to separate groups and species by means of obscure 

 specific differences in the structure of organs and parts of the body. 

 The antennae, mouth parts, and sclerites or plates of the body are usu- 

 ally employed, but such a mass of technical terminology has, of necessity, 

 piled up on this account that the ordinary student of Coleoptera is 

 much mystified. 



The eggs of beetles are laid where the larvae, upon hatching, will find 

 an abundance of food suited to their needs. It may be on leaves, twigs, 

 decaying logs, carrion, fresh water, or underground. The larvae are 

 known as grubs, wireworms, water-tigers, and the like. They usually 

 possess six thoracic legs (some species have more), biting mouth parts, 

 and simple eyes. The larval life lasts from a few weeks in some species 

 to three years in others. After several molts they change into pupae, 

 either underground or in or on the food, using the last larval skin as a 

 pupa case, or constructing a rough cocoon of earth and bits of wood 

 and vegetable matter. 



Only such of the eighty families as possess especial interest or eco- 

 nomic importance can be treated, even briefly, in a short discussion. 



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