670 THE STUDY OF INSECTS. 



sons, have gained an idea of what goes on in a single nest. 

 There are two broods each year. The mature bees of the 

 fall brood winter in the nests. 



The Large Carpenter-bee, Xylocopa virginica (Xy-loc'o-pa 

 vir-gin ; i-ca).— This is a large insect, resembling a bumblebee 

 in size, and somewhat in appearance. But it can be easily 

 distinguished from a bumblebee, as the female has a dense 

 brush of hairs on the hind leg, instead of a basket for carry- 

 ing pollen. This bee guilds its nest in solid wood, and some- 

 times excavates a tunnel a foot in length. These tunnels 

 are similar to those of the carpenter-wasp, Monobia quadri- 

 dens (Fig. 788) ; but differ in being provisioned with a paste 

 of pollen and nectar, and in the structure of the partitions. 

 These are made of chips of wood, securely cemented to- 

 gether, and arranged in a closely-wound spiral. This 

 arrangement of the chips is easily seen when the lower side 

 of a partition is examined ; but the upper side of a partition, 

 which forms the floor of the cell above it, is made concave 

 and very smooth, so that the arrangement of the chips is 

 not visible. 



II. THE GUEST-BEES OR INQUILINES. 



Although bees are proverbially industrious, we find 

 many loafers in the family. We do not refer to the lazy 

 males of those species in which the females are hard workers, 

 but to certain species in which both sexes are alike idle, 

 and dependent upon the exertions of other species of bees. 

 These idle species are called guest-bees, or inquilines, be- 

 cause they are reared in the nests of other bees, who act, 

 willingly or unwillingly, as hosts. 



The guest-bees are entertained both by solitary bees and 

 by social be'es ; but each species of guest-bee inhabits the 

 nests of a particular kind of working bee. Thus the nests 

 of certain bees are visited by certain guest-bees, while those 

 of other species are infested by different guests. This habit 

 of sponging their living has had a degrading effect on the 

 guest-bees ; for we find that they are not merely idle, but 



