NORTH AMERICAN HYMENOPTERA. 
49 
Desoriptioii!4 of new species of North Annericaii Bees. 
BY CHARLES ROBERTSON. 
ANDRENA. 
In the study of the mutual relations of flowers and insects I have 
found many insects which I could neither determine myself nor get 
determined by others. Conspicuous among these are the species of 
Andrena. In order, therefore, to get names for use in my biological 
work, I have undertaken to describe as best I could the species which 
occur in my neighborhood. Some of them may have been described 
before, by Smith, in British Museum Cat. Hym. and in New Spec. 
Hym. Brit. Mus. After careful study I have been unable to deter- 
mine more than two of Smith’s species. The fact that a specimen 
agrees in every detail with Smith’s description would not, to my 
mind, establish the probability of its being the same as its type. His 
descriptions are limited almost entirely to the colors of the pubes- 
cence, which is variable and liable to fade. Thus, of the twenty-four 
female specimens of A. Cressonii, only three show the normal color 
of the pubescence. The color of the surface is also very variable. 
The abdomen sometimes varies from entirely red to entirelv black. 
Sets of specimens in which the legs are commonly black, with the 
apical joints ferruginous, often show individuals having the tarsi, the 
middle tibiae at tips, and the hind tibiae entirely ferruginous. 
In all, or most of the species, the ground surface is minutely rough- 
ened. Unless there is a distinct punctuation in addition to this, I 
call the surface impunctate. One trouble with Smith’s descriptions 
is that one cannot always be certain whether he refers to this minutely 
roughened surface or to a distinct punctuation. 
Of the twenty-six species of Andrena mentioned in this paper, I 
have both sexes, except in five cases. I have taken the sexes of 
eleven species in copula. These bees can best be collected by watch- 
ing flowers of willows in Spring and of Composite in fall. The 
females should be identified first and the males referred to them. 
I submit a synopsis of all the species which occur in my neighbor- 
hood (Carlinville, 111.) with notes on their time of flight and the 
flowers which they visit, as well as descriptions of the new species. 
Besides those given below I have ten sets of specimens which indi- 
cate the presence of several additional species. 
TKANS. AM. ENT. SOC. XVIII. 
(7) 
.\PKIL, 1891. 
