Insects 207 



sexes hatch out during the summer, but the males die in the 

 fall, whereas the females winter in the ground, and come out in 

 the spring or early summer to make their nests, unhampered by 

 the unemployed males. One species visits Evening-primrose 

 flowers after sundown. 



(13) Andrena differs from Halictus in being larger on the 

 average, with the basal nervure not distinctly or conspicuously 

 arched. The females have peculiar depressions, the facial foveae, 

 at the sides of the face and the front close to the eyes. They are 

 best seen when looked at from above. The species are even more 

 numerous in Colorado than those of Halictus, 1 19 being on record. 

 This is probably due to the fact that many are oligotropic, or 

 associated with particular plants, while few Halictus are thus 

 restricted. The Rev. F. D. Morice of Woking, England, is a well 

 known student of bees. When I visited him several years ago he 

 led me round his garden, and pointed out how he had planted 

 different wild flowers, each to attract some species of Andrena 

 which flew in the vicinity. A Colorado naturalist could do the 

 same thing, by planting Oregon-grape, wild gooseberry, willow, 

 yellow violet, and so forth. 



(14) Colletes is a genus of bees with short, broad bilobed 

 tongue, adapted for lapping. The species are of moderate size, 

 and may be taken for Andrena if the mouth parts are not ex- 

 amined. There is however a good character in the wings; the 

 large cell below the second and third cubitals bulges outward at 

 the end, instead of being squarely cut off, as it is in most bees. 

 The Colorado Colletes at present number sixteen, but it is certain 

 that more remain to be described. They are adapted to get 

 nectar from only very shallow flowers, but sometimes they ob- 

 tain it without paying for their meal, that is, without doing any- 

 thing to cross-pollinate the flowers. It was noticed that many 

 blue Mertensia flowers had a large hole in the tube, cut by some 

 bee with its mandibles, to get at the nectar. After much watch- 

 ing, the culprit was found, it was Colletes nigrifrons, a short 

 tongued bee which could not otherwise obtain nectar from tubular 

 flowers. 



(15) Hylaeus (also called Prosopis) has 21 Colorado species, 

 small black insects, usually with conspicuous markings on the 

 face. They are not noticeably hairy, and do not look like bees. 



