HYMENOPTERA 



267 



the body. Some of them, however, may be confused with some of 

 the wasps, from which they may be separated by the structure of the 

 first segment of the hind tarsus (which is dilated, flattened, and 

 usually provided with numerous hairs 

 to aid in carrying pollen) and also by 

 the fact that the body hairs are covered 

 with short branches instead of being 

 simple, as in wasps. They are quite 

 variable in habit : some are solitary, 

 that is, each female makes a nest for her 

 young, as do the solitary wasps ; others 

 lay their eggs in the nests of other bees ; 

 while others, of which the honey-bee is 

 the best example, live in colonies. The 

 nests may always be recognized, how- 

 ever, by their being stored with pollen 

 and honey and never with insects. Two 

 families are recognized, which are dis- 

 tinguished by the length of the tip of 

 the labium, or glossa. 



In the Short-tongued bees (Andre- 

 nidae) the tip of the labium is shorter 

 than the base, while in the Long-tongued 

 bees (Apidae) it is much longer and en- 

 ables them to secure the nectar from 

 deeper flowers. All of the bees are of 

 great economic importance, for as they 

 go from flower to flower the pollen be- 

 comes attached to the hairs of the body 

 as well as to the special structures on the 

 legs, by which they transport it, and is 

 brushed off on the stigma of the next 

 flower visited. Thus the bees are the 

 most important agents in the cross-fer- 

 tilization of flowers, without which many plants will not set their seed 

 or fruit. For this reason those who grow cucumbers and tomatoes 

 under glass always have a hive of bees to fertilize the flowers, and 

 where bees are scarce, many of our common fruits set but sparingly. 



FIG. 425. Nest of Andrena, 

 the mining bee 



(After Packard) 



