126 BEES AND WASPS [OH. 



become too dry they shrivel and die, or at any rate 

 are crippled on emergence ; on the other hand if kept 

 too wet they are apt to suffer from attacks of mould. 

 It is safest therefore to keep them in a cool place 

 through the winter, and only to expose them to 

 warmth as the season for natural emergence draws 

 near. For this purpose a warm room is better than 

 direct exposure to the sun, from which in their 

 natural surroundings they are, of course, always 

 screened by the surrounding soil or wood fibre, as 

 the case may be. When the insects do emerge they 

 should then be placed where they can enjoy the 

 sunshine and dry the hairs on their bodies, for these 

 are at first generally damp and more or less matted 

 together. Some of these insects live for more than 

 one season in the immature state: hence, if the 

 imagines do not appear in the first summer, it is 

 often worth while to keep the specimens in their 

 boxes through a second winter on the chance of 

 emergences taking place in the summer following. 

 One of the most satisfactory results of rearing 

 specimens in this manner is the ease with which 

 many parasitic insects and "cuckoos' 1 among the 

 Hymenoptera themselves may with certainty be 

 assigned to their several hosts. To secure this end 

 the nests must, of course, either be kept each in a 

 separate box, or a simpler method may be adopted, 

 namely that of wrapping each bit of bramble stem, 



