H. C. FALL. Ill 



wanting, the surface more shining than usual. The introniittent 

 organ of the male is subcylindrical, blunt, and rounded at the tip 

 instead of flattened, and rather suddenly acuminate, as in the other 

 sections. 



Sexual difl^erentiation here reaches its greatest development. In 

 the male the beak is shorter, dilated at the base, and more strongly 

 sculptured. The first joint of the antennae is generally shorter, the 

 second bears near the base, on the upper side, several closely-placed, 

 minute setie, which, under moderate power, have the appearance of 

 a small denticle. The front thighs are more or less swollen or 

 tuberculate on the inner face toward the tip; the inferior, and to a 

 greater or less extent, the lateral surface of the swelling is polished, 

 the polished area being often marked by parallel longitudinal striae, 

 which differ in coarseness and approximation in the different species. 

 The thigh is usually distinctly longitudinally concave or grooved 

 beneath at the tip, the concavity limited externally by a more or less 

 well-defined ridge. The femoral swelling becomes nearly or quite 

 obsolete in a very few species, but the polished area beneath is always 

 evident. The front tibse are rather suddenly though not very strongly 

 widened at about the basal fourth, the middle and the hind tibise are 

 armed at the tip with a small mucro which is frequently almost con- 

 cealed by the terminal spinules. The metasternum bears, near the 

 middle of the posterior margin, two rather distant, small, acute tuber- 

 cles or spinules, which are sometimes faintly indicated in the female. 



The tips of the elytra are frequently conjointly produced into a 

 more or less prominent lobe in the female. 



This group has proved by far the most troublesome of the four, 

 and I cannot reasonably hope to have discovered in all cases the 

 true specific limits. It is quite possible that the sexual characters 

 used are not as constant as they are assumed to be, and only the 

 patient study of accumulated examples from carefully recorded 

 localities can remove the doubts which must accompany any arrange- 

 ment based on the limited material now in collections. 



Of four species — protensiDn, atripes, anceps and qaadrlcolle — 

 females only have been seen ; these species must, therefore, be 

 considered as tentatively placed for the present. 



The following table is the best I am now able to ofi'er : 



Front tbighs with a conspicuous tubercle in the % 1. 



Front thighs ( %, ) merely swollen toward the tip. 4. 



Front tbighs ( % ) not or scarcely perceptibly enlarged. 5. 



TRANS. AM. ENT. SOC. XXV. OCTOBER. 189H. 



