Coloration and Development of Insects. 71 



and if its galls be like those on ■\Yillo^YS, &c., they would 

 have, at least, a general resemblance to the reddish 

 markings on the caterpillar, and the similarity between 

 the two may serve to hide the caterpillar when the berries 

 are unripe or absent, or even when they are present. 



II. FoRTHER Notes on the Coloration or Saw-Fly 

 Larv^. * 



a. On the Changes of Colour undergone hy certain Larvce. 

 — It has long been known, from the observations of 

 Beaumur, De Geer, and many modern observers, that 

 many saw-fly larvas, immediately before pupating, change 

 colour, becoming, as a rule, more obscurely and uniformly 

 coloured, and throwing off any hairs, spines, &c., which 

 they may have carried before. What is the meaning of 

 this change ? It might be said that in the case of a spiny 

 larva it was in order to give it greater freedom to spin the 

 cocoon, but obviously this answer will not explain why 

 spineless larvas change. The change of coloration is most 

 conspicuous with gaudily-coloured larvae, as, for instance, 

 with the gooseberry grub, whose two forms of larva are often 

 taken for two distinct species. All gaudily-coloured larvre 

 do not change colour; while, on the other hand, others, 

 whose coloration is obscure, do so, although in this case 

 the diiference between the two is not very conspicuous. 

 Unfortunately, our knoAvledge of the habits of these 

 creatures in a state of nature is still somewhat limited, 

 especially as to their modes of 'pupation. We cannot 

 suppose that the change is altogether useless and meaning- 

 less, and I believe further observation will shoAV that it is 

 protective, either in concealing the creature, or by making- 

 it more conspicuous in the case of noxious larvce. Saw-fly 

 larvce are seldom large; protected larvce therefore can 

 only make their presence known by feeding in company 

 on a leaf; but when they become full-fed they have to 

 separate, to descend to the earth to seek a resting-place, 

 and while doing so they encounter new enemies, and are 

 exposed to dangers of a difterent kind from what they had 

 been accustomed to. Hence a change of colour might be 

 of advantage ; either a colour which would simulate the 

 surroundings, or one which would make them more con- 

 spicuous than they were when living in companies. While 

 some of these creatures bury themselves immediately 



* See Trans. Ent. Soc, 1878, p. 141. 



