﻿242 THE ENTOMOLOGIST. 



surface of the larva is pale green. Between this pale green under 

 surface and the dorsal and lateral surfaces the fleshy filaments 

 arise ; they are pinkish brown in colour, and, as the larva lies 

 closely attached to the stem of its food-plant, these filaments 

 embrace it on either side, and thus help very materially to render 

 the insect like a swelling in the stem. This is the invariable 

 position of the larvae when at rest. The larvae in cage 2 are, on 

 the average, considerably behind the others. They feed chiefly 

 on the opening buds of the food-plant ; they are somewhat paler 

 in colour than those fed on Aristotelia. 



On November 3rd, the larvae in cage 1 were preparing to 

 descend into the earth, while the others were just passing their 

 last moult ; so that it can be safely said that the Leptospermum 

 had had the effect of retarding the majority of the larvae to the 

 extent of one moult behind those fed on the more succulent and 

 nutritious Aristotelia. 



The difference in colouring between the two lots of larvae 

 thus treated were, however, of the most trivial description; and 

 I must say that this somewhat surprised me at first, as I had 

 often taken the caterpillars of Declana floccosa from both plants 

 in a state of nature, and observed the greatest divergence between 

 them, those off the Leptospermum being a very pale ochreous 

 brown, while those from the Aristotelia were very much darker, 

 and often mottled with grey, like the stem of the plant. I am 

 inclined to think that these differences have been gradually 

 brought about by the larvae feeding on the same plant for many 

 generations, and thus the protective resemblances have been 

 inherited and constantly improved through natural selection 

 acting on each lot separately. I should mention that Lepto- 

 spermum and Aristotelia do not generally grow near one another. 

 The former plant is found in dry situations, such as the sides 

 and tops of hills ; while the latter grows in the damp gulleys, 

 generally on the borders of streams. This circumstance would, 

 of course, tend to prevent two races of Declana floccosa — one 

 feeding on Leptospermum and the other on Aristotelia — from 

 interbreeding, and thus the larval peculiarities adapted to each 

 food-plant would naturally become still more pronounced. The 

 imago of D. floccosa is extremely variable in a state of nature, as 

 the following table will show : — 



Var. 1. — Which I assume to be the type, has the fore wings pale 

 greyish white, with numerous small brownish black streaks, exhibiting a 

 slight concentration towards the tip of the wing. 



Var. 2. — Has, in addition, several large round spots on disc of fore wing. 



Var. 3. — Has numerous black spots on fore wings (formerly known as 

 D. nigrosparsa). 



Var. 4. — Has two conspicuous curved lines on fore wing from costa to 

 inner margin (formerly known as Declana junctilinea). 



