BEETLES. 



393 



r,:,.~ll!ldm- 

 poruif rotundatus. 



ma. 474. —Hiili- 

 plusfasctfifas. 



and North America. The species of Ai/nhiis, Mutus, and Ilybius are all soniewliat 

 similar ill appearance to 7^/irt«<««', and most of the species are about the same size. 

 Coptotomiis Interroyatus is very common in the eastern United States. It is about 

 (1.35 of an inch lony, the elytra are somewhat irregularly striped longi- 

 tudinally with yellow, and the ))rothorax is banded transversely with 

 the same color. 



In Ili/drajjuriis, a genus which contains over seventy-five described 

 North American .species, the prosternum is deflexed between the front f 

 coxte, the anterior and middle tarsi are apparently four-jointed, the 



scutellum is not visible, and the metasternum attains the mesosternum. 

 The s)iecies are all of comparatively small size. 



The faniilv IIai.iim.ii>.k, often united with the Dytiscidre, includes a 

 small number of minute, sub-a(|uatic C'oleojitera, which are oval and 

 very convex, and whicli swim ])oorly. They are yellow, S])otted with 

 black. Their jnetasterniirii has an aute-coxal jiiece separated by a dis- 

 tinct suture, and their antenna' :nr ten-jointed. 

 The Cakabid.e nuudter j>robably (]\-er ten thousand descril)ed species, \arying in 

 size from very minute forms up to beetles from twu to three inches in length. Drs. 

 Le Conte and Horn give the following characters by which species of this family can 

 be readily distinguished from other adephagous coleoptera : Metasternum with an 

 ante-eoxal [liece, gejiarated by a well-marked suture, reaching from one side to the 

 other, and extending in a triangular pi-occss lietween the hind cox;e ; eleven-jointed 

 antenna' arising at the side of the lii.'ad, betwi'en tlie l)ase of the m.-nuiibles and the 

 eyes; hind coxie mobile and sim]ile; and habits terrestrial. These beetles have 

 slender legs, and run rapidly ; the wings are often poorly developed. On account of 

 their rajiid running haliits, the (4erm:nis ti'rni tliest' ('oleojitera " Laufkafer." Sonoritic 

 organs are not common in insects of this family, l)ut species of lilethi.'ia and of 

 ]£liijjjirus stridulate. Luminous organs liav<' been re)iorted in tjie case of Phi/soderu 

 noctilucu from .I.ava. 



A large numlier of Caraljida- li:i\i' .'inal gl.-mds, which have been mistaken by some 

 writers for urinary organs, but which aic il(fensi\ e in function. The muscular bladder- 

 like receptacles of these glands ai-e two in number, one on each side of the terminal 

 portion of the intestine, and each opens just above the rectal opening. Into these 

 receptacles, which serve to store the defensive fluid until needed, ojien the ducts of the 

 glands which prejtare the secrt'tion. In most cases the secretion is an odorous acid 

 liquid, which can be s))urteil out (juite a distance, and Pelouze lias shown that, in cer- 

 tain s])ecies of ('(indni.'i, this secretion contained liutyric acid, the sanu' aci<l that 

 imparts its indescribable oilor to rancid butter. In Jirachinus and a feu- 

 other genera the secretion of the anal glands is either ji.'U'tly gaseous on 

 emission, or becomes a ])ennanent gas inuuediately afterwards, as can 

 be readily jiroved by comjielling one of the insects to <lischarge its secre- 

 tion underwater beneatli an inverted test-tube filled with the same licpiid. 

 In this way I liave collected, in a few monu'Uts, from Aptinus disploaor, ^^^^. 4-, _/j,.„^.;„ 

 a Pyrenean species related to JJnit:hiniit<, an amount of gas equal to sc 



iiusfiimnits, iKiiu- 

 bnrUitjr beetle. 



eral times the space occupied by the beetle itself. The discharge of the 

 anal glands of lirachinas, often rapidly re|>eated when the beetle is held between the 

 fingers, is accompanied by a smoke-like vapor and a popping sound, whence insects of 

 that genus are pojiiilarly termeil bombardier-beetles. 



