ON THE PHYSICAL POWER OP INSECTS. 237 



The most curious part of the Wasp's nest is the material of which it is made, 

 the whole 1 being constructed of a very durable kind of paper, made by the Wasp 

 from the raspings of decaying wood. Early in summer I have frequently watched 

 them on wooden rails and fences exposed to the weather for two or three years, 

 busily engaged scraping the surface with their powerful mandibles. It thus 

 collects a small pellet of matter, which it reduces into fine fibres (after the man- 

 ner of our paper-makers), and then mingles with it a gum which it secretes for 

 the purpose ; a substance is thus formed which, when spread out in thin layers, 

 hardens, and becomes a paper well fitted to withstand the changes of the summer 

 weather. The Wasp was thus certainly practising the art of paper-making ages 

 before men were acquainted with this valuable process. 



Spiders, although not strictly speaking insects, are still often associated with 

 them. Their works are well deserving the attention of the lover of Nature. 

 The geometric net of Eperia diadema, although framed for no very benevolent 

 purpose, is one of the most beautiful works produced by the labours of any of 

 the lower animals. When carefully examined it will be found that not one of 

 the numerous stays that stretch them out are superfluous. They have engaged 

 the attention of naturalists with a view to explain their mode of projecting those 

 fine threads (see Vol. II. , p. 376) ; when it was found that their emission could 

 not be accounted for by a projectile force in the spinner, the aid of electricity 

 was called in to answer for the cause, as it has often before been employed to 

 explain what was imperfectly understood ; but a few well-conducted experiments 

 have shewn that the Spider possesses no power of shooting a thread unless aided 

 by a current of wind ; this any one may prove experimentally, by placing a 

 Spider on a small straw fastened only at the lower end, and surrounded \p 

 water ; put a bell glass over the insect to keep off" air, and it will be found alto- 

 gether unable to escape ; but when a current of air passes over the Spider it 

 immediately elevates itself and gives out a thread which is rapidly drawn along 

 by the wind. From time to time the Spider tries with its foot to see if the 

 thread has caught any object ; when it does find the end of this thread fastened, 

 it immediately makes use of the bridge of rope thus formed to escape, or if the 

 current be sufficiently strong it will commit itself to it when the rope is long 

 enough to bring the insect up. 



Spiders have the credit of possessing a good foresight as to the changes of the 

 weather ; it is remarked, that many more long streaming webs are found in fine 

 settled weather than when the weather is changeable, but it is evident that much 

 of this may be due to the bad weather destroying more rapidly the works of these 

 little labourers, than to their foresight in meteorological matters. 



The labours of the numerous varieties of caterpillars are extremely interesting ; 

 they are also often very destructive. The time of their entering into the pupa 



VOL. III. — no. xx. 2 K 



