72 Mr. P. Cameron on the 



beneath the food-plants, others travel some distances, in 

 order to find a suitable resting-place. This is especially 

 the case with those which do not pupate in the earth, but 

 bore into the stems of pithj'- plants, in lieu of spinning a 

 cocoon, or because the cocoon itself is thin. Some of these 

 species (EmpJiijtus, Taxoims) I have found at considerable 

 distances from their food-plants in stems ; and I have found 

 a cocoon of Lophyrus pini in a crevice' of a wall many 

 yards' distance from any pine. The view that the change of 

 coloration is protective is confirmed by observations I have 

 made on two very difiercnt species, and the observations 

 are especially interesting, as they illustrate the two forms 

 of protective coloration. While in most cases the change 

 is (as already mentioned) in the direction of a more 

 obscure (generally green) coloration, in one or two instances 

 the opposite is the case. There is a gall-making Nematus 

 found abundantly along the banks of rivers on Scdix p>ur- 

 purea. Living, as the creature does, in its larval state 

 concealed in galls, it has no need of bright colours, and 

 accordingly its body is white. At the last moult, however, 

 it becomes entirely slate-coloured, and leaves the galls for 

 the ground. I once found several of these larvre on the 

 sands which surrounded the trees, marching up to a higher 

 portion of the river bank. I noticed especially that the 

 colour of their bodies harmonised admirably with the sand, 

 and thus they were very difficult to see ; certainly a white 

 larva would be much easier detected. Another species of 

 the same group is found on Salix aurita. In this case, of 

 course, the comparison with the sand does not hold, but 

 then the slate colour agrees quite as well with the dead 

 grass, &c., found in the marshy situations where the species 

 lives. The other observation relates to Cladius viminalis. 

 Three or four of its larvas feed, ranged in a row, on the 

 underside of a poplar leaf, of which they eat only the 

 epidermis = When very young they are entirely green; 

 gradually orange makes its appearance on the first and last 

 segments, black marks appear on the body, which is also 

 covered Avith hair ; but still the green largely predominates. 

 Then at the last moult every trace of green disappears, and 

 the entire body is orange, save the black head and the black 

 marks. The brilliant colour acquired when it has stopped 

 feeding and is ready for pupating is explainable, I think, 

 by a reference to the habits of the creature. Living 

 several on a leaf, their presence is made sufficiently visible 

 during the greater part of their life ; but when they have 



