INSECTA 503 



solitary in habit. In these, the abdominal petiole is smooth (Fig. 346 C) 

 and, in species with a worker caste, this is always winged. The pro- 

 thoracic tergum extends back towards the wing base. Among solitary 

 species may be mentioned Odynerus which stores with caterpillars 

 its nest in which its larvae are developing. Pompilid wasps are ex- 

 clusively predatory on spiders. Certain forms have adopted the 

 "Cuckoo" habit, laying their eggs in the nests prepared and pro- 

 visioned by other species. Thus the ruby wasp Chrysis usurps the 

 nest of Odynerus. Mutilla behaves similarly towards many solitary 

 bees and wasps and has been bred out from the puparia of the tsetse 

 fly. Social wasps, e.g. Vespa, live in nests commonly constructed of 

 paper obtained in the form of wood pulp by these insect architects. 

 The larvae living in closely arranged cells on horizontal combs are 

 fed on insect food gathered by the workers. In early summer, our 

 common social wasps are useful in the control of such insects as plant 

 lice, etc. Later in the season, however, their liking for sweet fruits 

 may make them a nuisance both in the garden and in the home. In 

 autumn the colony perishes, fertilized females being the only sur- 

 vivors. Vespa germanica and Vespa vulgaris are common English 

 wasps. Vespa crabro is the Hornet (Fig. 341). 



Closely resembling these are those wasps belonging to the super- 

 family Sphecoidea, the distinctive feature of which is the possession 

 of a prothoracic tergum which does not extend back as far as the wing 

 bases. These are all solitary predaceous forms, which sting their prey 

 and so paralyse it before placing it in the larval cells which have been 

 previously prepared, e.g. Sphex. A tendency towards the social habit 

 is exhibited by Bembex which leaves its larval cells open and so can 

 provision its young from day to day on small flies. 



The super-family Apoidea includes the social and solitary bees. 

 Distinctive of bees are the dilated hind tarsi and the plumose hairs 

 of the head and body to which pollen adheres. Inner metatarsal 

 spines of the posterior legs comb the body hairs free of pollen, this 

 being then transferred to the outer upturned spines (pollen basket) 

 of the hind tibia of the opposite side. These legs are further adapted 

 by possession of special spines for the manipulation of wax plates 

 when being removed from the abdomen. The median glossa is also 

 characteristic and in certain solitary forms, e.g. Anthophora and all 

 the social bees, e.g. Apis and Bombus, is greatly elongated along with 

 the parts other than the mandibles^ for gathering nectar from deep- 

 seated nectaries of flowers. Larvae are fed exclusively on pollen, 

 nectar and salivary fluids. Megachile, the leaf cutter, is a solitary bee 

 which makes cells of neatly cut leaf fragments. Each cell containing 

 an egg is stored with honey and pollen. Such cells are commonly 

 made in the walls of houses, the mortar being removed for this purpose. 



