414 INSECTA. 



Acanthocerus, Mac Leay. 



First joint of the antennae very large, dilated superiorly and lami- 

 niformj the edges of the intermediate leaflet of the club, when it is 

 bent, are exposed. The tibiae, the four last particularly, are lamelli- 

 form and cover the tarsi, folding over them when the leg is con- 

 tracted. The epistoma tapers to a point or terminates in an angle. 

 The thorax is almost semilunar( l). 



There, or in our second division of the Arenicoli Trogides, Mac 

 Leay the antennae, scarcely longer than the head, are always com- 

 posed often joints, the first of which is large and very hairy. The 

 ligula is entirely concealed by the mentum. The labrum and man- 

 dibles are but little exposed, and the latter are thick. The palpi 

 are short. The mentum is entirely pilose. The inner side of the 

 maxillae is armed with teeth. The cinereous or earth-coloured body 

 is very scabrous or tuberculous above. The head is inclined, ter- 

 minates in an angle or narrows to a point. The thorax is short, 

 transversal, without a lateral border, sinuous posteriorly, with pro- 

 jecting anterior angles. The abdomen is large, arched, and covered 

 with very hard elytra. The anterior legs advance, and their thighs 

 cover the under part of the head. These Insects produce a stridu- 

 lus noise by the reiterated and alternate rubbing of the pedicle of 

 the mesothorax against the internal parietes of the thoracic cavity. 

 They are found in earth or sand, and appear to gnaw the roots of 

 vegetables. They form the genus 



Trox, Fab. Oliv. 



From which, under the generic name of Phoberus, M. Mac Leay, 

 Jun., has separated those in which the sides of the thorax are de- 

 pressed, dilated and bordered with spines, and which are destitute 

 of wings. On each side of the posterior edge of the thorax is a deep 

 emargination; the epistoma is rounded anteriorly(2). 



(1) Mac Leay, lb. p. 136; A. wneus, a species for the knowledge of which I am 

 indebted to one of our most able naval engineers, and not less excellent entomo- 

 logist, M. Lefebure de Cerisy. M. Mac Leay refers the Trox spinicornis, Fab., to 

 the same genus. 



(2) Trox horridus, Fab ; Mac Leay, Hor. Entom., I, 1, p. 137. The species of 

 Trox, Fab., remain where they are. See this author, Olivier and Schoenherr. 



The genera Cryptodus and Maschidius, arranged by Mac Leay in his family of the 

 Trogidae directly after that of Phoberus, have the posterior extremity of the ab- 

 domen exposed, and nine joints in the antennse, characters which appear to re- 

 move them from Trox. I suspect that the Machidii, from the form and emargina- 

 tion of the labrum and from some other characters, are allied to the Melolonthae. 



