77. THE NOTODONTINA. 97 



Its colour is pale yellow striped with brownish-pink near the segmental divisions. It is very active, 

 and does not devour the egg-shell after emergence. 



The full-grown larva has the body much flattened underneath. In colour it is pale brownish- 

 pink, with numerous irregular darker markings, which in some specimens almost form two broad sub- 

 dorsal lines. The under surface of the larva is pale green. There is a series of fleshy filaments 

 of a pinkish-brown colour along each side of the insect, and an extra pair of prolegs on the ninth 

 segment. 



This caterpillar is, however, very variable, its colouring appearing to depend largely 

 cm its surroundings. The favourite fond-plants are Leptospermum ericoides and Aristotelia 

 racemom. The larva' found on the former plant are usually pale yellowish-brown, whilst 

 those from the latter are much darker brown, often mottled with grey like the stems of the 

 Aristotelia. A specimen 1 once found on a mountain beech (Fagus cliff ortioides), the 

 gnarled stem and branches of which were covered with grey lichens and mosses, was 

 mottled with the most beautiful shades of greenish-grey. These larval varieties are very 

 interesting, and in order to test the direct influence of food on the colouring of the larva?, 

 I once divided a batch of eggs deposited by a single female into two equal parts, and fed 

 one half on Aristotelia, and the other half on Leptospermum. The differences in colouring 

 between the two lots of larva' thus treated were, however, of the most trivial description. 

 This somewhat surprised me at first, as I had previously observed quite distinct varieties 

 on each plant, when found in a state of nature. Hence I am now disposed to think that 

 these differences have been brought about gradually, by natural selection acting on larva' 

 feeding on the same plant lor a huge number of generations. By this means a sufficient 

 amount of variation might be accumulated, to cause the closest possible approximation in 

 colouring to the stems of the several food-plants. It is also noteworthy that many of 



these f l-plants grow in widely dissimilar localities, so that the free inter-breeding of insects 



dependent on them would not be likely to occur, and thus the peculiarities of colouring 

 adapted to the stems of each food-plant would not be disturbed by the effects of inter- 

 breeding. 



In connection with the foregoing experiment it is also interesting to observe, that 

 the specimens fed on Aristotelia matured much more rapidly than those on Leptosper?num; 

 the former plant evidently being the more nourishing food for the larva'. Also that out 

 of the batch led on Aristotelia 28 became moths, of which 12 were males and 10 females ; 

 whilst out of those fed on Leptospermum only -24 became moths, of which 15 were males 

 and '.) females. In all other respects, excepting food-plant, the two lots of larva 1 were 

 subjected to identical treatment. 



During the day this larva rests quietly attached to the stem of its food-plant, where 

 it is very difficult to detect, as the filaments so closely embrace the twig or tree-trunk that 

 the whole insect exactly resembles a swelling in the stem. 



The pupa of JD.floccosa is enclosed in a loose cocoon on the surface of the ground. 



The perfect insect appears about September, and continues in more or less abundance 

 until the end of April. There are most likely several broods in a season, and, as we 

 frequently meet with specimens of the moth on mild days in the middle of winter, it 

 probably also hibernates. 



This insect is usually observed at rest on fences and tree-trunks, where its grey 

 mottled colouring causes it to closely resemble a patch of lichen. 



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