i8o MEMOIRS ON THE COLEOPTERA 



but smaller and still more close-set. In Euetheola rugiceps Lee., 

 there are no granules, but the corresponding surface has a system 

 of close-set and excessively minute points, so minute in fact that I 

 cannot surely determine whether they are raised points or punctula- 

 tion ; at any rate, they scarcely have a sound producing function. 

 In Ligyrodes the mentum is convex, gradually depressed basally, 

 setose only along the sides and the ligula is broad and broadly 

 truncate; the median tooth of the mandibles in typical Ligyrodes 

 is larger and longer than the two lateral and is generally somewhat 

 obliquely truncate. There are two subgeneric groups as follows: 



Mandibles tridentate externally; head moderately small, with a trans- 

 verse, medially interrupted ridge; clypeus more or less narrow at 

 apex; sterna punctate and pubescent; pronotum never indented. 



Group I 



Mandibles bidentate at tip, more slender; head much larger, with two 

 widely separated tubercles, the apex of the clypeus broadly truncate, 

 the two teeth remotely separated; sterna glabrous and almost im- 

 punctate; pronotum with a minute apical tubercle in front of a small 

 oval indentation Group II 



I am not at all certain that some of the general characters stated 

 above, particularly those relating to the spiracles and stridulating 

 organs of the typical Ligyrodes relictus type, apply to the large 

 tropical forms placed in the second group, my material being too 

 scanty for investigation : 



Group I. 

 Subgenus Ligyrodes in sp. 



This subgenus is represented by a moderate number of species, 

 some of which are abundant individually in the subarctic parts of 

 North America, excepting the Pacific regions, and extending south- 

 ward along the interior table lands to or beyond the City of Mexico. 

 It is therefore essentially a subarctic group and is much more cir- 

 cumscribed in habitat than Ligyrus, or even Euetheola. The apex 

 of the post-coxal prosternal process has a flattened and explanate, 

 densely ciliate part and a bulbous nude anterior part, a formation 

 frequently observable in the Cyclocephalini. The various taxo- 

 nomic forms are rather well differentiated and most of those 

 announced below are probably true species, though some may 

 ultimately find a place as subspecies: 



