166 NEOTROPICAL PSELAPHIDAE 



From the above references it will be seen that this genus has been given 

 considerable attention, and second, that between the original description of the 

 genus by LeConte in 1880 and the final congeneric elucidation by Raffray in 

 1904, the genus in its modern sense was not understood, the neotropical species 

 being known under some four different names; as late as 1896, Raffray placed 

 a Mexican species, clavicornis, in the purely Australo-Asiatic Eupines. 



At the present time this important genus includes American species only, 

 having in common: (1) short, globular to subglobular body, (2) ventral surface 

 of head with a median, longitudinal carina, (3) maxillary palpi not abnormally 

 formed, but simple and regular, (4) antennae eleven-segmented, often ab- 

 normal, (5) pronotum with neither lateral nor median foveae, in rare cases a 

 minute, indistinct punctiform basal impression (injlatus), (6) each elytron with 

 four punctiform foveal points replacing the basal foveae, and with no trace of 

 a dorsal stria, (7) abdomen with a relatively long first tergite, and the first two 

 to three tergites distinctly, but narrowly margined, (8) first sternite invisible 

 medianly, and wholly covered at this point by the metasternum, (9) inter- 

 mediate coxae distant, the mesosternum advanced between them as a flat, trun- 

 cate plate, (10) posterior coxae very distant. 



The males generally have the epistome diversely elevated and anned, but 

 this is not an absolute criterion since some species have the epistome simple in 

 the male, and in other species only the male sex is known. The antennae are 

 usually abnormal in the male sex, but again this is not an absolute criterion. 

 In one group the males have the second segment of the anterior tarsi expanded. 

 Sex, then, is best determined by either direct dissection, or by examination of 

 the genital structures in cleared microscope slide-mounts. On triangle-mounts 

 specimens having the epistome or antennae abnormal, or both, are probably 

 males. The metasternum may be either concave or convex in the males. 



The genus is of interest to the zoogeographer. At present there are eighteen 

 known species. The genotype, horni LeConte, is North American, distributed 

 from southern California to Arizona, and is presumably derived from the Mex- 

 ican fauna. Of the remaining seventeen species, three inhabit the Lesser Antilles, 

 three inhabit South America from the Amazon drainage basin to high elevations 

 in Bolivia, one at the cross-roads in the Panama Canal Zone, and the remaining 

 ten are found from Guatemala and British Honduras to Vera Cruz, Mexico. If 

 these species are all really congeneric, then Mexico, especially Yucatan with 

 at least four species, would seem to be the center of distribution, with one migra- 

 tion route to the north-west into the arid southwestern United States, a second 

 through the Canal Zone into South America, and a third over a now submerged 

 connection with the Antilles. Much expeditionary work needs to be done before 

 a clear picture can be presented. It should be noted that the related Berdura, as 

 well as the Hybocephaline Ephimia among others, have species found in the 

 Lesser Antilles and the Canal Zone. In Scalenarthrus the genus in general is 

 Central American, with Antillean as well as South American and North Amer- 

 ican exponents. 



