NO. 1487. NORTH AMERICAN DIGGER WASPS— FERNALD. 307 



The articulations of the hind cox* with the body are close together 

 and at the very posterior end of the under surface of the thorax, the 

 coxte projecting- distinct!}^ backward. The ti'oia is slightly longer 

 than the femur and its hinder surface is coarsely sericeous, almost 

 pubescent. In some cases the inner side of the hind tibia is suddenly 

 swollen near the end, though the segment usuall}' only gradually 

 increases its diameter in going out from the body. At the end of 

 the tibia are two long spines, one of which has been modified to form 

 a cleaning apparatus. The outer edge of this spine is nearly straight, 

 but its inner edge for the third of its length nearest the tibia rapidly 

 increases and apparently is formed by ver}" closely set hairs. The 

 rest of the inner edge bears a row of stiff hairs or teeth, longest near 

 the middle. The differences in the structure of this inner edge are 

 useful in suligeneric determinations. The hind metatarsus is usually 

 straight. In one case {P/'otero.sjjhex tepanicum. Saussure), however, it 

 is noticeably curved near its base. The tarsus as a whole is like those 

 of the other legs. (Plate VI, figs. 3, 4.) 



Sexual distinctions. — Aside from the presence of a sting in the 

 females and of more or less evident copulatqry organs in the males, 

 many differences ma}^ frequently be noticed in the two sexes. In the 

 females the antennae are composed of 12 segments while in the males 

 13 are present, and show several longitudinal ridges, as already 

 descril)ed. The inner margins of the eyes generally converge down- 

 ward in the males. The outline of the anterior edge of the clypeus is 

 more strongW developed, a tarsal comb is absent, the outline of the 

 hinder end of the al)domen is less pointed than in the females and 

 more abdominal plates are present and are of a different form, the 

 clothing of the bodv is generally more developed and in the species 

 here treated the male is smaller than the female. 



CLIMATIC VARIATION. 



Variation in members of the Chlorioninse in relation to climate is not 

 very marked. Certainly the more highh" colored forms are from the 

 tropical and subtropical regions, while black is more prevalent in 

 northern examples, but no striking differences in this regard are 

 noticeable. In a general wa}", however, it may be said that in species 

 showing varying amounts of black and ferruginous the black covers 

 more of the surface and that the ferruginous is less rich and strong in 

 northern than in southern specimens. Pubescence in amount and in 

 richness of color has also the same characters. In northern examples 

 there is less of it and it is usually rather pale, while in insects from 

 the Southern States, Mexico, and the West Indies it becomes more 

 abundant, often forming a dense covering for almost the entire body 

 except the abdomen, and its color is much deeper and richer. In one 

 or two cases colors other than those usual to the group appear, as in 



