22 BKITISH BUTTERFLIES. 



Salle also describes (Ann. Soc. Ent. France, 1857, p. 20) gregarious 

 Mexican larvae that he observed, living on the branches of a small 

 Arbutus, one suspects that his reference is also to this species. Our 

 own Aporia crataegi, a species approaching to this Eucheira group, 

 alone of our European Pierids, shows real gregarious tendencies, 

 accompanied by abundant silk-spinning. Its nest is well-formed, and 

 used most regularly both for shelter and rest until after hybernation, 

 i.e., from July to April, and, to some considerable extent, after the 

 larvae have recommenced to feed in the spring, but there is no attempt 

 to approach the habits of Eucheira and its allies, in the later larval 

 stages, by making a still more effective silken nest for the purpose of 

 pupation, but, on the contrary, the larvae of A. crataegi become quite 

 solitary in their last stages, although they still spin plenty of silk to 

 enable them to keep their footing, and pupate, in true Pierid fashion, 

 by means of an anal pad and body girth. The Australian Pierid, 

 Delias harpalyce, is also gregarious, spinning an extensive web on 

 Loranthus pendulus, essentially, however, to give a safe footing, but 

 being used, also, when the larvae are fullfed, as a base for attachment 

 before pupation. 



As to the meaning of gregarious larval habits, those species known 

 to us appear to have at least four or five objects in view : (1) To make 

 a safe carpet for their travels. (2) To afford a safe hiding-place when 

 not feeding. (3) To make a safe retreat during the moulting period. 

 (4) To make an adequate hybernaculum. (5) To make themselves 

 conspicuous, so that their tints become, in the mass, effective as 

 warning colours, and their movements equally so. The origin of 

 gregariousness had, no doubt, also, as one of its essential factors, the 

 economical use of silk, etc., either as a carpet, or as cover, although 

 there were, presumably, other powerful inducements. 



There can be no doubt that almost all gregarious larvae find 

 the silken web a great advantage in getting from one part of their 

 food to another, without possibility of being lost, particularly when 

 small. This is well illustrated if one observes the young larvae of 

 Pieris brassicae, which have to travel over leaves with smooth 

 glabrous surfaces, and whose not abundant silk-spinning becomes 

 much more effective in association than would be the case if 

 they travelled singly. The gregarious habits of young larvae of 

 Melitaea aurinia, M. cinxia, etc., similarly enable them to spin a 

 useful path, uniting the somewhat distant leaves of their foodplant 

 together, and thus save them from the many possible dangers that 

 might occur if they lived solitarily, and had to descend to the ground 

 and climb up the farther parts of their foodplant for a meal. There 

 can be no doubt whatever as to the effectiveness of the widely-spread, 

 thin, spider-web-looking carpet spun by these larvae in the autumn, 

 and a similar purpose is no doubt served by the extensive webs spun 

 by the young larvae of Aglais urticae, Vanessa io, and continued to 

 maturity by the larvae of Eugonia polychloros and Euvanessa antiopa. 

 The journeys necessary for these species, and also for Aporia crataegi, 

 should the larvae be dislodged, especially when young, by winds or 

 storms, would be very great, and a possibility of much loss is un- 

 doubtedly thus prevented by enabling them to travel safely from one 

 part of their foodplant to another, without descending and reclimbing 

 to a new position, as well as enabling them to maintain a firm footing 



