THE GREGARIOUS HABIT IN BUTTERFLY LARViE. 13 



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 of Lycaenid, is known to be social, living in 

 numbers within the fruit of the pomegranate." The latter suggestion 

 is traversed by Niceville (Butts, of India, iii., pp. 477-481). 



If we restrict ourselves to our better-known British butterfly 

 species, we may note the difference in the social habits in the three 

 groups presenting this phenomenon, viz., the Pierids, Vanessids, and 

 Melitaeicls. In the former, the eggs of Pieris napi are laid solitarily, 

 and the larvae are quite solitary in habit; those of Pieris rapae are laid 

 in small batches, and one rarely finds this larva quite solitary in its 

 younger stages, and a loose social condition is sometimes noticeable 

 even in tbe adult larvas ; the eggs of Pieris brassicae are laid in large 

 clusters, and the gregarious habit is strongly maintained throughout, 

 but no web is spun, except a slight one for footing, either in the 

 earlier or later larval stages. In all these species, however, hybernation 

 is passed in the pupal stage. In the somewhat allied Aporia crataeyi, 

 however, the eggs are laid in a cluster, the newly-hatched larvae imme- 

 diately spin a web, into which they retire for the purpose of resting, 

 and in this they hybernate during the winter. Soon after they recom- 

 mence feeding in the spring, they distribute themselves, and finally 

 give up entirely their gregarious habits. 



The various stages exhibited here are recapitulated, as it were, by 

 the Vanessids inhabiting this country, e.g., Pyrameis cardui and P. 

 atalanta live a purely solitary life. Polygonia c-album usually lays 

 several eggs (one on the other) on a plant, and several larvae, at least 

 when young, live in close proximity. Aglais urticae lays her eggs in 

 masses of from 100-250 eggs, the larvae from their birth spinning a 

 web, in which they live in the most strictly gregarious manner, 

 enlarging their web with growth, until, in their penultimate skin, they 

 leave the protection of the web and spread abroad for food, although, 

 even in this state, two or three may often be seen on the same or 

 adjacent leaves. Vanessa io acts very similarly. But the allied 

 Eugonia polychloros and Euvanessa antiopa spin larval webs, less, how- 

 ever, for hiding purposes, it would appear, than as ropes leading from 

 one part of a branch of their foodplant to another, retaining their 

 gregarious habit to the end, the common and conspicuous web form- 

 ing a safe footing on their lofty habitations in windy and stormy 

 weather. 



The larvae of the final group of gregarious butterflies in this country, 

 the Melitaeids, have, in at least our two best- known British species, 

 Melitaea aurinia and M. cinxia, strictly gregarious habits, at least till 

 after hybernation, restricting themselves to the area covered by the 

 common web in their wanderings, and accumulating en masse for 

 purposes of rest and shelter. After hybernation, the gregarious habit 

 largely passes away with the first moult, although the larvae are often 

 found in numbers in close proximity, even up to the time of pupation, 

 Goodwin also notes (in litt.) that the larvae of M. athalia are gregarious 

 until after hybernation, and pass the winter in a web. 



It is a remarkable fact, and one tending largely to show the 

 antiquity and fixity of habit in species, that the larvae of those species 

 noted above, that are common to both the Palaearctic and Nearctic 

 areas, have retained their habits absolutely unchanged, although the 



