BEETLE, (AS. lit el, betel, literally 'biter,' from lUan, Engl. lite). An insect of the order Coleoptera. which seems to be wingless when at rest, but really possesses two pairs of wings. At rest one pair is folded beneath two horny cases that fit over the back and meet in the median dorsal line. These homy cases are the elytra or wing-covers, which are only the modified forewings ; and they distinguish beetles from all other insects save the earwigs, which are easily separable upon other grounds.
The slight protection afforded by this armature seems to be very advantageous to beetles, for they form the largest order of existing insects. "In bodily form," says Dimmock, "the Coleoptera present every variation from long cylindrical to nearly globular, from hemispheres to extremely flattened disks, from straggling ant-like forms to compact seed-like ones." AH, nevertheless, ex- hibit a division of the body into three parts, which, however, are not the typical head, thorax, and abdomen, but a modification of these — head, prothorax or fore body, and mesothorax and nieta thorax combined with the abdomen into a hind body.
The Hcnd bears various appendages, and the mouth opens forward or dowTiward. The mouth parts are strong, equably developed, and adapt- ed both for gnawing and for seizing prey. The mandibles are large and strong, and in the males of some forms reach a great size. (See Stag Beetle.) The Curculionidae, or snout beetles, have a long beak, but it is a prolonga- tion of the liead infront of the eyes, and not of any of the mouth parts.
The eyes are compound, and usually large and eflfective, except in a few cave-dwelling species. (See Cave Animals.) Ocelli are absent, aa a which may thus see what is going on both above and below the surface of the water as they swim. The antenn;^ ( most commonly eleven- jointed) are placed just in front of the eyes, and are organs not only of touch, but of smell and probably of hearing. They appear under a variety of forms, some of whioli are pretty con- stant throughout large groups, giving them such names as elavicorn. lamellicorn, serricora, longi- corn, etc. "The antennte are said to be clavate when thickened at the extremity, in the form of a club or knob; lamellate, when three or more of the terminal joints spread out in broad proc-
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FOUMB OF .WTENN.E OF BEETLES. SPrrate ant^nnie and modiflcatioiis: 1, Si'i-rute (Ludius) ; 2, Peotinate (Corymbite.'i) ; 3, Bipectinate (Prionoc.vpboa) ; 4, Flaljellate (Acneus) •, 5, Plumose (Dendriiides) : 6, 7, 8, Irregularly Serrate, approaching Clavifortn (Clavat* Antennie); 9, Trogosita; 10. Oatoptrii-liua; U. Colon; 12. Bryaxis: 13, Anogdua; 14, Liodee; 15, Epierus; 16. Ph.v- maphora: 17, Heterocerus; 18, Adranes, Capillary and Verticillate; 19. Moniltform (Dasyeerus): 20, Lamellate (Rliyasodes) ; 21, L>icanus; 22, Bolbocerus ; 23, Irregular (La'chnosterna) ; 24, Dineutes.
rule, in the adult form, even where possessed by the larv'«. The compound eyes vary greatly in form and appearance and number of facets, and sometimes are divided into upper and lower parts, so that the insect is really four-eyod; this is especially the case in some water beetles, HEAD OF A BEETLE.
Arrangement and names of mouth-parts: a, I^abium ; b, Labial palpus; c. c. Maxillip: d. rf, Maxillary palpi; e, e, Eyes: f, f, .Antennte (1, pedicle: 2. scape; 3, flagellum) ; ff.
Mandibles; b. Mentum; >, Submentum; j, Gula. esses which lie flat upon one another; serrate, when the joints have on one side short angular processes like the teeth of a saw; pectinate, or comb-like, when the processes are fairly long and stand out nearly at right angles; or flabellate, if the processes are proportionately very long." It is believed that the senses of smell and hear- ing reside in the antenna'. The former is evi- dently well developed in most, if not all, beetles, while the latter .seems certainly possessed by many. The tapping of such species as the 'deathwatch' implies a listener of the same kind ; and similar evidence is furnished by the fact that longicorns and some other beetles are often capable of producing sound by stridulat- ing or rubbing together various external hard parts of the body, such as wings and legs, or surfaces and angles on the prothorax and meta- thorax; they produce some tones that man is incapable of hearing. These organs are pos- sessed chiefly by the males ; and a rfsume of facts relating to it and to many other char- acteristics distinguishing the sexes of beetles mav be found in Chapter X. of Darwin's Descent of Man (London, 2d ed., 1874).
The Fore Body forms the second well-marked division of a beetle, and consists of the pro- thora.x, which in Coleoptera is not united solidly with the two other thoracic segments, but con- nected movably with them. "Its tergite (prono- tuni) is a very prominent feature in all beetles, reaching back to the origin of the elytra." It is hollowed forward to receive the head, and in some groups it is modified in form or possesses horns and spines of extraordinary appearance. These, as a rule, are seen only in the males, however, and most prominently among the lamellicoms. This fore body wears the fore- most pair of legs, with which tlic hinder pairs may or may not agree. Beetles use their lega more tlian their wings. They do fly, but lesa frequently and skillfully than they run, jump.
