278 H. C. FALL. 



The presence or ahsence of a moderately deep longitudinal groove 

 on the pronotum has offered a ready means of dividing our species 

 into two priuiary groups. The division is apparently a natural one, 

 inasmuch as there are several concurring differences in structural 

 details, which, although suffering some exceptions, are so constant 

 as to be regarded as group characters. Dr. Horn lias already 

 called attention to one of these, viz.: that in the species with sulcate 

 thorax the hind claws are very nearly simj)le. One of the forms 

 described here as new (decolorata) is exceptional in that the poste- 

 rior claws are cleft in nearly the same degree as prevails throughout 

 the other group. 



Again, in the group with sulcate thorax, the spurs of the poste- 

 rior tibiae, except in pu-nlla, are mutually equal in length in the 

 male, and nearly so in the female, and, as a rule, are sexually 

 modified ; while in the non sulcate series the posterior tibial spurs 

 are distinctly unequal in length and exhibit almost no sexual modi 

 fications. Tiie impression on the outer side of the terniinal joint of 

 the maxillary palpi, which, in the non-sulcate species, exists as an 

 elongate oval, slightly flattened area, becomes in the sulcate species 

 distinctly excavated. Two exceptions in each series, however, must 

 be noted ; muscula and nana having the joint distinctly impressed, 

 while decolorata and pusilla show scarcely a trace of it. 



There is usually not the least difficulty in recognizing the sexes, 

 LeConte says "The males are more slender in form than the 

 females, and are distinguished by the club of the antennse being as 

 long as the funiculus." To this Horn adds that " the abdomen 

 viewed in profile from the side, is convex along the median line in 

 the female and concave in the male." With the exception of clij- 

 peata, and possibly of pallens (males of which have not been seen), 

 the above characters hold good throughout our series. 



A more exhaustive examination enables me to ad<l several other 

 less conspicuous sexual differences which apply almost as genei'ally, 

 but in somewhat variable degree. In the nuiles the eyes are usually 

 noticeably larger and more prominent; the terminal joint of the 

 maxillary palpi is freciuently broader and more widely truncate at 

 apex ; the anterior tibiie are less strongly produced, and the poste- 

 rior thighs are more slender than in the female. The sexual differ- 

 ence in the last joint of the maxillary palpi is well shown in elo)t- 

 gata, subvittata, testacea, diluta and fuscula, and is quite obvious in 



