AMERICAN COLEOPTERA. Ill 



sexes are nearly alike in form, and the fourth ventral segment much 

 longer. In none of our species is the fourth tarsal joint bilobed, as 

 it is said to be in some European species, nor does this structure 

 obtain with us in any of our genera of this tribe, though feebly 

 approached in Niptinus. 



In an arrangement of species, the subgenus Ptinus should precede 

 Gynopterus, the short fourth ventral segment, the oval elytra in the 

 female, with the accompanying short metasternum, and the habits 

 of a number of the species allying them naturally with the preced- 

 ing genera. In Ptinus there is great uniformity in most details of 

 structure, but good characters exist in variations of bodily form or 

 vestiture, which enable the species to be separated without much 

 difficulty when both sexes are at hand. In Gynopterus, as repre- 

 sented with us, there is less uniformity among the species as a whole, 

 but there is a central homogeneous group, represented by 4 niacula- 

 tus and interruptus, which is diffused throughout our territory from 

 the Atlantic to the Pacific, and extends into Mexico and Central 

 America, and which appears to be peculiar to this continent; at 

 least I have seen no European analogue. Nearly all. the difficulties 

 encountered in the study of our species center in this group, in which 

 the tendency to form local races, even within the same faunal area, 

 renders the determination of specific limits a matter of great diffi- 

 culty. A careful study of the material at hand enables me to define 

 nine species, divisible into two unequal subgroups, the first contain- 

 ing ^.-maculatus and prolixus distinguished by the very elongate male 

 antennae with filiform joints ; the second containing hystrix, eximius, 

 texanus, interruptus, concurrens, fallax and vegrandis, in which the 

 antennae in both sexes are subserrate. Throughout the genus there 

 are more or less pronounced sexual differences in the size of the eyes 

 and length of the antennae, and in the true Ptinus we may add 

 form of body and sometimes vestiture. In Gynopterus, with the ex- 

 ception of a small apical ventral tubercle in the males of certain 

 species of the interruptus group, I have observed no secondary sex- 

 ual characters other than the universal ones above mentioned. The 

 primary sexual characters are so far as studied practically identical 

 within the limits of each subgenus, but differ so conspicuously from 

 each other as to suggest their separation as distinct genera. 



In Ptimis the side pieces of the male genitalia are sennmembran- 



TKA.NS. AM. ENT. SOC. XXXI. MARCH, 1905. 



