384 William Mortoti Wheeler 



genera of bees, have a greater amount of yellow or white on the 

 face or clypeus or on both than the cospecific females. Stylopiza- 

 tion tends to diminish this light color yery perceptibl\ and hence 

 to make the face of the male resemble that of the female. In the 

 female the parasites produce the reverse effect, making the face 

 resemble that of the male. "It is difficult to find a stylopized 

 male of A. labialis, e.g., whose face is normally colored and, on 

 the other hand, it is quite as rare to find a stylopized female of 

 this species having the face entirely black." (2) The normal fe- 

 male Andrena differs from the normal male in the structure of its 

 hind legs, the tibi:c of which are modified for collecting pollen. 

 They are always robust and incrassated and have a brusli of long, 

 curved hairs, especially on their internal surfaces. Similar hairs 

 are found also on the femora, coxip and metapleurDe. The metatar- 

 sal joint of the hind legs is also kilated or enlarged and is furnished 

 with rows of stifi^ hairs on its lower surface. In the male the hind 

 tibiit and metatarsi are slender and bear only short, sparse, straight 

 hairs and this is true also of the coxae and metapleurae. The pres- 

 ence of Stylops in the abdomen of the female diminishes the de- 

 velopment of the pollen-collecting apparatus to such a degree 

 that the hind legs become like those of the male. The reverse 

 occurs in stylopized males, the organs under consideration be- 

 coming more enlarged and approximating to the female type in 

 their pilosity- The modifications in this sex, however, are rarer 

 than in the female and in both sexes they vary greatly in different 

 stylopized individuals. (3) The frontal furrow near the internal 

 orbit of the eyes, which s filled with velvety pubescence, is well- 

 developed in the normal female, but feeble or absent in the normal 

 male. In stylopized Andrenae this furrow may undergo diminu- 

 tion of development in the female and becomes accentuated in the 

 male. (4) Although the female Andrena has 12-jointed, the male 

 13-jointed antennae, there is no modificationof the numberof joint 

 in parasitized individuals. The antennae of the normal sexes may 

 differ in the length of the second funicular joint. In one species, 

 A. Trimmeriana, the second funicular of the normal female is as 

 long as the two succeeding joints taken together, whereas in the 

 normal male this joint is at most half as long as the succeeding 



