INTERRELATIONS OF INSECTS 287 



female eggs in worker or queen cells, and male eggs in drone cells; but 

 the means by which she exercises control over the fertilization of the 



jggs is not understood. 



It is known that unfertilized eggs produce always drones, and at 



jresent it is generally believed by geneticists that drones never 

 come from fertilized eggs. The principal reasons for this opinion 

 are these: (i) if a pure-bred queen of one race is crossed with a drone 

 of another race, the female progeny (workers or queens) have hybrid 

 characters, but the male offspring have only characters of the maternal 

 race; (2) eggs from worker or queen cells contain spermatozoa; those 

 from drone cells do not. 



BUMBLEBEES 



Familiar as the bumblebees are, their habits have been little studied 

 in this country, though in England "bumblebees" have formed the 

 subject of an interesting volume by Sladen. The queen hibernates and 

 in spring starts a colony, utilizing frequently for this purpose the 

 deserted nest of a field mouse or sometimes the burrow of a mole or 

 gopher. The queen lays her eggs in a small mass of pollen mixed with 

 nectar (Putnam) . The larvae eat out cavities in the mass of food and 

 when full grown spin silken cocoons, from which the imago cuts its 

 way out; the empty cocoon being subsequently used as a receptacle for 

 honey. At first only workers are produced and they at once relieve the 

 queen of the duties of collecting nectar and pollen, caring for the young, 

 etc. The workers are of different sizes, the smaller ones being nurses 

 or builders and the larger ones foragers the kind commonly seen out of 

 doors. In the latter part of summer both males and females are pro- 

 duced, but when severe frost arrives, the old queen, the workers and the 

 males succumb, leaving only the young queens to survive the winter. 



SOCIAL WASPS 



The Social Wasps constitute the family Vespidae, of which we have 

 three genera, namely, Vespa , Polistes and Polybia, the last genus being 

 represented by a single Californian species. 



Vespa. Some species of Vespa, as V. maculata, make a nest which 

 consists of several tiers of cells protected by an envelope (Fig. 288), at- 

 taching the nest frequently to a tree; other species, as germanica and 

 vulgaris, make a nest underground. The paper of which the nests are 



