Insects and their world 



Social Hymenoptera — wasps^ bees^ ants 



Wasps and bees exist at all levels, from a solitary life to the most highly 

 organised social life in a nest, but the truly social species are very much 

 in the minority. In North America, out of nearly 5000 species of native 

 bees, about 50 species are truly social. These comprise the familiar 

 bumblebees and the well-known honey-bee. A similar situation exists 

 with the stinging wasps. 



Wasps 



Adult wasps live on sugary foods, but their larvae are carnivorous, 

 and have to be supphed with animal food. The solitary wasps (Fig. 60) 

 either make burrows in sandy soil, or build earthen cells attached to 

 twigs. In suitable patches of sand the burrows of 'fossorial' wasps (and 

 bees) may be congregated together, but this is a community like that 

 of the ant-lions, we have mentioned above, and not a social group. 



The adult wasp provisions its nursery cell by catching an insect and 

 stinging it until it is immobilised, though not killed. The family 

 Sphecidae burrow in the ground and use a single caterpillar to feed their 

 young. The Pompilidae catch a spider and also put it into a burrow in 

 the soil. The Crabronidae catch flies and pack them away in large 

 numbers, either in the ground or in rotting woodwork: it is startling 

 to find that a window-frame or a doorpost is rotten inside, and tenanted 

 by a mixed lot of wasps and flies. 



When the food is provided and an egg is laid, the cell is usually 

 sealed off and left to look after itself. Some wasps, however, continue to 

 supply food after the larva has hatched, and this is possibly a hint as to 

 how maternal care and true social life may have evolved. 



The true social wasps are the familiar yellow jackets, bald-faced 

 hornets, and the imported Giant Hornet of the East coast. Others 

 include the Polistes wasps which differ from the hornets in their more 

 slender abdomen and exposed nests. The fertilised females, or queen 

 wasps, spend the winter in sheltered places, and can be seen on warm 

 spring days, restlessly searching for a suitable nesting-place. They 

 choose a hollow of some kind, in the ground, or in the roof of a porch 

 or outhouse, and there build a comb of cells from 'wasp-paper' — a 

 sort of papier-mache made from wood chewed with saliva. 



The larvae that hatch from the eggs are fed with portions of other 

 insects, previously chewed up by the adult wasp. At first the queen 

 feeds her brood, but the adult wasps that develop from it are sterile 

 females and take on the duties of workers. They now do all the cell- 

 building and foraging, and leave the queen to concentrate on laying 

 more and more eggs. 



The wasps that are a nuisance in the late summer and to picnickers 



100 



