FAMILY HABITS IN BUTTERFLY LARVAE THE PIERIDS. 51 



are said to live socially, when young, like those of P. brassicae, 

 collecting together on leaves of Tropaeoliun, but scattering before 

 the last moult, after which they live singly. The main habits of 

 the lame of the Pierid species are : (1) The purely summer-feeding 

 habit exhibited, all the species hybernating as pupae. (2) The 

 tendency to develop " forwards " and " laggards " in direct response to 

 the meteorological conditions of the particular season producing one, 

 two, or three broods, or partial broods. These points are noticeable in 

 all our British species — P. brassicae, P. rapae, and P. napi. (3) The 

 silk-spinning habit, most probably to obtain a safer footing on the 

 usually very glabrous leaves of their various foodplants. 



The manner in which the larvae of our common Pierids devastate 

 their foodplants is known to everyone. They devour everything, often 

 leaving only the main stems of the leaves of whole fields of vegetables, 

 e.g., cabbage and its allies, and frequently do great damage. In 

 North America, where Pieris rapae has been introduced, it is almost 

 equally destructive, and Edwards observes (Butts. North America, 

 vol. i) that Pieris virginiensis has exactly similar habits. He notes that, 

 "when young, the larvae of this species are green in colour, and that keen 

 sight-is required to discover them ; at this time they attack the leaves of 

 certain garden vegetables, making small holes, returning to the margin 

 of the hole from time to time, till all the surrounding parts are eaten 

 away. The large leaves of horse-radish maybe seen entirely consumed 

 in this way, leaving but the skeleton untouched. When at rest, the 

 larvae lie extended upon the surface of a leaf, generally along one of 

 the ribs or in a depression, and, as they retain their green colour to 

 maturity, they are effectually screened from notice." 



The habits of the larva of the Nearctic Pieris oleracea are very 

 similar to those of P. napi. Scudder says (Butts. New Engl., p. 1199) : 

 " It eats small round holes throuoh the leaves of its Cruciferous 

 foodplants when young, making larger and less regular ones as it 

 matures. It feeds mostly at night, and remains at rest during the 

 day, frequently standing in the groove made by the midrib on the 

 upperside of a cabbage- or turnip-leaf with its head towards the base 

 of the leaf .... spinning silk for a foothold. It returns to the 

 same place upon a leaf day after day ; moving about but little, 

 crawling very slowly, with its mouth to the surface on which it is 

 crawling, placing there a silken thread to aid it in clinging. . 

 The larva, at all times, feeds to repletion, so that the skin of the 

 body is tense and glistening when it has finished a meal. It never 

 eats the leaf at the edges, and generally, or always, leaves the veins 

 untouched, feeding upon the undersurface only." This description 

 will be seen to apply very fairly to our own Palaearctic species, and 

 Scudder's further note on P. rapae (op. cit., p. 1210) that "the young 

 caterpillar eats small patches in the parenchyma of the underside of a 

 leaf, and later feeds exposed, usually on the underside of a leaf, and 

 devours the whole leaf, except the harder veins," and that, " when the 

 plants are ' headed,' it works its way up from below in disconnected 

 passages, so that the leaves are riddled in every direction, etc.." will be 

 recognised as being as true of P. rapae in Europe as in North America. 



As in the allied Palaearctic species, the Nearctic Pieris oleracea 

 also is single-, double-, or triple-brooded, according to latitude; thus, 

 it is recorded as having only one brood in Labrador, two in Newfound- 



