BEETLES. 303 



an extraorcliiinry size, nml are sometimes branclied. Beneath tlie manrlililes are the 

 maxilL-p, wliieli ai-e more ilelieate and more eomplex tlian tlie maiuliljles, and whieh 

 aid the latter in mnstieatinp-, njiparently jiei-t'ormini;- the Uuhter and more eomplieated 

 part of the work. The liasal artieuhition of eaeh maxilla is termed the eardo, to this 

 is attaeheil the sti]ies, with an external seale-like seument, the sqnama palpig'era ; to 

 the sijuama paipi'^era a mnltiarticiilate jialjms, the ])nlp\is maxillaris, or maxillary 

 palpns, is jointed. Two lamellar lobes, the real ehew iiiii-orpans of the maxilhe, are 

 also attached to the npper edge of the stipes ; these are termed, respeetively, the lobns 

 cxternns, and the lobns internns. In the Cieindelida\ Carabida;, and Dytiseida^, the 

 lobus extermis is jialpiform and nsnally two-joiuteil. The maxillary palpi generally 

 have fmn' joints. Beneath or l:)ehind the m.axilhe is, homologically, a third ]iair of 

 buccal org;ms, a second ]iair of maxilhe, the two halves of which are united together 

 at their bases, which latter are also iniited above with the ligula or tongne, and Ijelow 

 form the mentuni or chin. The ligula and mentum, the last of which articulates with 

 the lower portion of the head by the gular suture, are im]iortant in the classitication 

 of Coleoptera. .Toine<l to each side of the ligula is a jialpus labialis, usually three- 

 jointed. A membranous ]n'oeess nsnally exists on each side of the ligula near its tij) ; 

 these processes are the paraglossR'. 



The labrnm above and the labiinn beneath, in Coleojrtera, as in other chewing 

 insects, are jiassive in function, serving to hold the food in place while it is masticated 

 by the mandibles and maxilhe. As the cheeks in higher vertebrates prevent a side- 

 wise or lateral s(pieezing out of the food from lietween the teeth, so the labrum and 

 labium of Coleojitera keej)S th(> food in its position between masticatory organs which 

 operate laterally. All the mouth-]iarts of adult Coleoptera arcv subject to slight modi- 

 fications and reductions in certain families and genera, and in the larv.a? the oral organs 

 are not rarely consiilerably modified. The larva' of Dytiscida' and Hydropliilida' pre- 

 sent remarkable modifications of form and use, which, as in the case of other striking 

 variations from the normal form of larval nn)utli-]iarts, will lie described under their 

 res]iective families. 



The prothorax, the middle of the three ]iortions into which all beetles are divided 

 with considerable distinctness, is hollowed out in front to receive tlie neck or liead, 

 and is articulated behind with the mesothorax. The ])rothorax bears the forward 

 legs. Its dorsal surface is often termed the |ii'onotum. 



The mesothorax, metathorax, and abdomen form the last of tlie three portions of a 

 beetle, which portion is often called the trunk. 



The mesothorax and metathorax are very intiinatelj' united ; upon the former are 

 borne the elytra and middle pair of legs, and upon the latter the wings and hind pair 

 of legs. Both mesothorax and metathorax are hidden from view, on the dorsal side 

 of the insect, by tlie elytra, except that in most beetles a small triangular jiortion of 

 the mesothorax is visible between the elytra at their bases; this triangle is the scu- 

 tellum. The median ventral ])ieces of the three different ])arts of the thorax arc 

 termed, resjiectively, prosternum, mesosternum, and metasternum, an<l the pieces 

 which connect each of these sternal pieces at the sides with the dorsal pieces, are 

 termed the episterna and epimera, respectively, of the prothorax, of the mesothorax, 

 and of the metathorax. The sutures betwei-n certain of the above-mentioned ]iarts 

 may be obliterated in some cases. 



The abdomen is broad anteriorly, is closely united witli the metathorax, is in most 

 cases entirely covered or protected from above by the elytra, and contains the sexual 



