384 ZOOLOGY 



cease to eat and turn to pupae in their cells. The imago 

 emerges in ten days, and sets to work to enlarge the nest. As 

 soon as the perfect insect vacates its cell, it is cleaned out and 

 another egg is deposited in it. 



During the first half of the summer, only workers appear, 

 but later males and females make their appearance, the former 

 from the parthenogenetic eggs of the later broods of workers ; 

 all these kinds are winged, but the workers are smaller than 

 the males and females. The sexes pair whilst flying, and 

 soon afterwards the males die. 



There are seven species of Vespa found in Great Britain ; 

 of these the hornet, Vespa crabro, is the largest. This does 

 not extend north of the Midlands ; its nest is larger than the 

 common wasp V. vulgaris, but its colonies contain fewer indi- 

 viduals. V. rufa has a reddish tinge on its legs; it, like 

 V. vulgaris and germanica, builds its nest in the ground, whilst 

 V. sylvestris, arhorea, and norvegica are tree-wasps, building 

 their Hests in trees. 



The other European genus of this family, JPolistes, occurs 

 round the Mediterranean. Its nest consists of a single layer 



Fig. 218. — Polistes tepidus and nest. 



of cells, forming a comb which is vertically or obliquely placed, 

 and is not covered in by an outer case, like the nests of the 

 various species of Vespa. 



Family Eumenidae. — Eumenes coarctata is the only British 



