256 DYXASTIN-H;. 



Subfamily DYNASTIN^. 



The Subfamily Dyxastix.e, although not one of the largest, is 

 one of the best known groups of Lamellicokxia, iucludiug many 

 of the largest and most striking of the beetles. It is very 

 scantily represented in the Oriental Kegion and its Indian repre- 

 sentatives number only forty-six out of a total of about a thousand 

 described species. Although closely related to the Cktoxiin'.i:, one 

 of the most remarkable for brilliant colouring among the groups 

 of Coleoptera, this on the contrary is one of the most sombre. 

 This, as would be supposed, implies a notable difference of habit, for, 

 Avhilst the foregoing Subfamily is in general conspicuously diurnal, 

 the Dyxastin.e generally remain in concealment by day and emerge 

 at night, when decorative effects could have no signiticauce. The 

 majority of species are black, and almost the only departure from 

 the rule occurs when by some deficiency of the black pigment shades 

 of yello\\", brown or red are produced. Even within these limits, 

 nothing in the nature of a pattern is found except in an American 

 genus, Cyclocephala, and a few other American species. These 

 exceptional members of the group are found to have exceptional 

 habits, being entirely diurnal and frequenting flowers like many of 

 the Cetoniin.x. A single Indian species, Chalcosoma atlas, the 

 largest of Indian beetles and one of the most striking, has a slight 

 greenish metallic lustre and is almost unique in that respect. 



The group is chiefly remarkable as that in which sexual 

 dimorphism appears in some of its most striking phases. Horns of 

 relatively enormous size occur, chiefly in the males, upon the head 

 audtliorax ; and as some of the species in which they attain their 

 maximum development are also among the largest existing insects, 

 they have naturally always attracted quite exceptional attention. 



Strvdure. 



Practically all the Dtnastix.e are winged, and in flight the 

 wings are spread in the usual way, so that the structure of the 

 elytra and the correlated parts of the thorax is not of the peculiar 

 type found in the Cetoxiix-i:. The scutellum is always exposed, 

 small and bluntly triangular, and the elytra completely cover the 

 abdomen, except the pygidium and generally part of the pro- 

 pygidium. The latter often bears a vocal apparatus, consisting of 

 tine transverse ridges capable of beiug drawn like a flle across the 

 sharp inturned posterior edge of the elytra by the movement of 

 the abdomen. The ridges are sometimes very long and cover the 

 greater part of the segment, which, moreover, may be considerably 



