SCARAB-EIDAE. 247 



in form; the surface is usually rough, and covered with a crust 

 of dirt, removed with great difficulty. Our species are numerous, 

 and belong to the genus Trox. The larger species having the 

 sides of the thorax not ciliate with hairs, were placed by Eriehson 

 as a separate genus, Omorgus ; but the characters, as observed 

 by Lacordaire, are indefinite, and it is not retained. 



The genus Trox possesses a distinct stridiilating organ ; it is 

 an elliptical plate, with pearly reflections, occupying the upper 

 part of the external face of the ascending portion of the first ven- 

 tral segment, and is covered by the elytra; on the inner surface 

 of the 'elytra, near the margin, about opposite the metathorax, is 

 an oval, smooth, polished space, which has probably some con- 

 nection with the stridulating organ. 



Sub-Family II.— MELOLONTIIIN^. 



This sub-family holds an intermediate position between the 

 Laparosticti and Pleurosticti. The second pair of abdominal spira- 

 cles is placed in the membrane connecting the ventral and dorsal 

 segments, as in other Scarabteidifi; in most species the third, and 

 sometimes the fourth, at the outer limit of this membrane; the lifth 

 and sixth pairs arc in the dorsal ])ortion of the ventral segments, 

 but the lines connecting them do not diverge strongly, as in the 

 Pleurosticti; the sevent i or last pair is usually visible behind the 

 elytra, but variable in position ; in other species, forming the first 

 two tribes, however, tlie spiracles are jjlaced as in the Laparosticti, 

 all being in the connecting membrane. 



The clypeus is usually prolonged and margined in front, so that 

 the mouth is inferior, but in Giaphyrini the mandibles iind hibruni 

 are prominc^nt; the mandibles are corneous, short, pyramidal; 

 the mentum large, quadrate, with the ligula usually corneous ami 

 connate with the mentum, though sometimes free and membranous, 

 as in the Laparosticti; the clypeal suture is usually distinct, trans- 

 verse; tiie antennae have from seven to ten joints, and the club is 

 always lamellate, sometimes consisting of six or five, but usually 

 of three joints, and is frequently longer in the males ; the tarsi 

 are always perfect, 5-jointed, with the claws variable in form, and 

 the bisetose onychium is present in all the tribes except Iloplini. 



The species feed exclusively on living vegetable matter, and it 

 will be seen that the distinctions between it and the other sub- 



