HYMENOPTERA 381 



As the larvae grow the queen adds wax to their covering, so that they 

 remain hidden. When the larvse are full-grown, each one spins around 

 itself an oval cocoon, which is thin and papery but very tough. The 

 queen now clears away most of the brown wax covering, revealing the 

 cocoons, which are pale yellow. These first cocoons number from seven 

 to sixteen, according to the species and the prolificness of the queen. 

 These cocoons are incubated by the queen, who spends much time sit- 

 ting on them, with her abdomen stretched to about double its usual 

 length so that it will cover as many cocoons as possible. 



The bees that are developed during the early part of the summer are 

 all workers; these relieve the queen of all duties except laying the eggs. 

 They feed the larvae, construct honey-pots and special receptacles for 

 pollen or store these substances in cocoons from which workers have 

 emerged. Later in the summer males and queens are developed; and in 

 the autumn the colony breaks up. A nest in midsummer is shown in 

 Figure 631. 



The bumblebees play a very important role in the fertilization of 

 certain flowers, as those of red clover, in which the tubular corolla is so 

 long that the nectar cannot be reached by bees with shorter tongues. 



The parasitic bumblebees, Psithyrus. — To this genus belong those 

 parasitic bees that infest the nests of bumblebees. They closely resemble 

 bumblebees in appearance and in structure,, except that, as in other para- 

 sitic bees, the females do not possess organs for collecting and carrying 

 pollen. Although the females of Psithyrus are easily distinguished from 

 those of Bombus by the absence of the pollen-baskets or corbiculae in the 

 former, the males of the two genera are very similar. In Psithyrus there 

 is no worker caste. 



Family Apid^e 

 The Honey-bees 



The family Apidae, as restricted here, includes only a single genus, 

 Apis, of which only four species are known, and one of these is doubt- 

 fully distinct. In this country a single introduced species, the honey- 

 bee, Apis mellifica, is found. This species has been widely distributed 

 over the world by man. 



This family consists of social bees in which the hind tibiae are without 

 apical spurs; the workers are furnished with pollen-baskets or corbiculae 

 on the hind legs, but the queens are without functionally developed ones. 

 Unlike the queen of the nest-building bumblebees the queen of the honey- 

 bee is unable to found a colony or even to exist apart from workers of 

 her own species. 



The honey-bee was introduced into America more than three centuries 

 ago, and escaping swarms have stocked our forests with it; for when 

 free, swarms almost invariably build their nests in hollow trees. These 

 nests include a variable number of vertical combs, which have cells on 

 both sides, instead of a single series as is the case in the combs of our 

 native social wasps. The cells of which the comb is composed are used 

 both for storing the food of the colony and for rearing the brood. 



The three castes of bees of which a colony is composed are easily dis- 

 tinguished. The workers are the well-known form that we see collecting 



