SPINiVING CATERPILLARS. 333 



In all the nests of social caterpillars, care is 

 taken to leave apertures for passing out and in. 

 It is remarkable, also, that however far they may 

 ramble from their nest, they never fail to find 

 their way back, when a shower of rain or night- 

 fall renders shelter necessary. It requires no great 

 shrewdness to discover how they effect this; for 

 by looking closely at their track it will be found 

 that it is carpeted with silk — no individual moving 

 an inch without constructing such a pathway, both 

 for the use of his companions and to facilitate his 

 own return. All these social caterpillars, therefore, 

 move more or less in processional order, each follow- 

 ing the road which the first chance traveller has 

 marked out with his strip of silk carpeting. 



There are some species, hov/ever, which are more 

 remarkable than others in the regularity of their pro- 

 cessional marchings, particularly two which are found 

 in the South of Europe, but are not indigenous m 

 Britain. The one named by Reaumur the proces- 

 sionary (^Cnethocamjjci processioned, Stephexs) feeds 

 upon the oak; a brood dividing, when newly hatched 

 into one or more parties of several hundred indivi- 

 duals, which afterwards unite in constructing a com- 

 mon nest nearly two feet long, and from four to six 

 inches in diameter. As it is not divided like that 

 of the brown-tails into chambers, but consists of one 

 large hall, it is not necessary that there should be 

 more openings than one ; and accordingly when an 

 individual goes out and carpets a path, the whole 

 colony instinctively follow in the same track, though 

 from the immense population they are often com- 

 pelled to march in parallel files from two to six deep. 

 The procession is always headed by a single cater- 

 pillar; sometimes the leader is immediately followed 

 by one or two in single file, and sometimes by two 

 abreast, as represented in the cut. A similar pro- 



