272 NATUEAL HISTORY. [CH. XLJ 



verdure of the foliage. Should the web, however, 

 be left till winter, it will have acquired a stronger 

 and tougher texture, so as to bear pulling off, which 

 should be preferred to pruning in certain cases, es- 

 pecially where it regards the fruit-trees. In short, 

 no other remedy will avail. When benumbing 

 winter arrives, they confine themselves entirely to 

 their silken habitation ; they then not only secure 

 the general web on all sides as strongly as they can, 

 to exclude impertinent intruders, but each individual 

 spins a thin case for itself. Here they rest in a 

 state of torpid security till the genial warmth of the 

 spring animates them afresh, and informs them that 

 the all-bountiful Author of Nature has provided food 

 convenient for them. Thus apprized, they issue 

 forth in the daytime and in fine weather, as before; 

 but having acquired stronger powers, and the foliage 

 they have now to encounter being more tender, 

 they become less scrupulous in their feeding, and 

 devour the whole of it. A disposition to associate 

 continues with them till they have changed their last 

 skins, when they usually separate, each endeavour- 

 ing to provide in the best manner for itself. At this 

 period many are attacked by the ichneumon-fly. 

 Some, however, continue together, when each spins 

 a separate web, in which it changes to a chrysalis ; 

 this usually takes place about the beginning of 

 June. It remains about three weeks in a state of 

 perfect quietude, when it changes in July to the 

 moth, which is perfectly white, except that at the 

 end of the abdomen is a tuft of brown down, with 

 which the female covers her eggs after they are 

 laid. 



The most probable causes of their appearance are, 

 the peculiarity of the weather, and the plenty or 

 scarcity of the enemies of the insect. As to the 

 former, warm and dry weather is universally al- 

 lowed to promote the generation of insects ; violent 

 winds, heavy and long-continued rains, or extreme 



