HABITS. 105 



caterpillars feed in rows upon the same leaf in 

 such close proximity that it would seem to inter- 

 fere with convenience. Sometimes this is the only 

 mark of their social nature ; but as all caterpillars 

 spin more or less silk in moving about, a web of 

 greater or less extent generally accompanies a 

 colony, and in some cases the community con- 

 structs a close structure, like that woven by the 

 Baltimore [Fig. 89], the caterpillars of which in- 



FIG. 89. Euphydryas Phaeton, nat. size ; under surface on right (Harris). 



close the whole tip of the plant on which the com- 

 pany feeds with a dense web [Fig. 90], within 

 which they retire to rest or to moult. A Mexican 

 butterfly, allied to our sulphurs, constructs a web, 

 first noticed by Hardy,* which is nearly as close 

 as parchment. With rare exceptions, all butterfly 

 caterpillars feed upon the outside of plants ; but 

 there are a few which live in the interior, and one 

 of these, an Indian species, is known to be social, 



* Travels in the Interior of Mexico. See also Westwood, 

 Traus. Ent. Soc. London, i., 38 (1834). 



