AMERICAN COLEOPTERA. 269 



stricted behind by the tarsal grooves. Ventral segments 1-4 

 slightly decreasing in length, first deeply excavated for the hind 

 legs and nearly concealed by them ; fifth subequal to the two pre- 

 ceding united. Ventral sutures deep, feebly or scarcely arcuate at 

 middle. Legs rather slender; tibise widest near the middle ; tarsi 

 short, stout, the first joint about as long as the next three. 



This genus is closely allied to the preceding — Eutylistus — but is 

 at once separable by its deeply incised eyes. The form is also more 

 rotundate, becoming almost globose in the majority of species. The 

 second joint of the antennal club, which, in Eutylistus and Dorca- 

 toma, is more or less broadly triangular, is here much narrower and 

 but feebly dilated apically. The small rounded prominence on the 

 outer edge at the base of the first joint of the front tarsi feebly fore- 

 shadowed in •Dorcatoma, and more distinct in Eutylidus, reaches 

 here its greatest development. The lateral striae of the elytra which 

 exhibit considerable variability in Eutylistus are practically invari- 

 able in Cvenocara, and consist of two nearly complete outer stria? 

 and a third inner basal stria which scarcely reaches the middle. 



Owing to the almost complete fixity or uniformity in the more 

 obvious external characters, the separation of species has proved 

 more than ordinarily difficult and has required an amount of study 

 entirely incommensurable with the importance of the genus as indi- 

 cated by the number of species involved. Fortunately, well marked 

 differences have been discovered in the form of the terminal joints 

 of the palpi and in the sexual modifications of the eyes and antennae, 

 and by these the species may be distinguished with a fair degree of 

 certainty. Once separated in this way, certain other more or less 

 obvious differences appear, which are, however, rarely sufficiently 

 pronounced in themselves to be relied upon. The surest means of 

 separating the sexes lies in the form of the first joint of the antennal 

 club. When both sexes are at hand this will be found to be invari- 

 ably more strongly produced inwardly in the males, the form in the 

 female being a slightly transverse isosceles triangle in all species. 

 In a large majority of species the terminal joint is sexually modified 

 but in a few species is not; the eyes are also larger and less deeply 

 cleft in the male in about half the species, but in the others scarcely 

 differ in the sexes. These variations were at first very puzzling, and 

 to make sure that the sexes had been properly separated the genita- 

 lia were extracted in nearly all species. The male organs are moder- 



TRANS. AM. ENT. SOC. XXXI. JULY, 1905. 



