78 BRITISH LEPIDOPTERA. 



Muscidae, with their apodous maggots, present the extreme of modifica- 

 tion though not of specialisation, and so with other apodous insects 

 and apodous Arthropods in general (Proc. Amer. Phil. Soc., xxxi., pp. 

 84-85). 



The resemblance of many lepidopterous larvae to a bird's dropping 

 is well known, and the same form of resemblance is often adopted by 

 many lepidopterous imagines (Ant'tthesia salicana, Cilix ylaucata, etc,). 

 So marked is this resemblance when the larva of Jocheaera alni is in 

 its fourth skin, that it is commonly known as the " bird's dropping " 

 stage. The young larva of Papilio machaon is similarly protected, and 

 Niceville says that " the young larvae of P. polytes, like those of 

 P. memnon, P. helenus and P. nephelits, have a strong superficial 

 resemblance to a bird's dropping, which doubtless greatly protects 

 them." 



When we see a Geometrid larva stiff and rigid on a twig, we are at 

 once attracted by the peculiar structure which enables it to maintain 

 its shape, simply by the pressure of the body-walls on the contained 

 fluids. We also observe how liable such a structure is to danger, and 

 thus, while we note how suited the lepidopterous larva is to exert a 

 great motive force at any movable point of its body-surface by means 

 of its fluid contents, we recognise also that its liability to injury must 

 necessitate some very successful expedients for its protection, if it is to 

 fight its way through the hosts of enemies which surround it. When 

 we examine a number of larvas, we find how rarely they are provided 

 with offensive structures, and, as a rule, lepidopterous larvae rely on 

 a purely passive defence, the most common of which is their resem- 

 blance to some part of their food-plant, such resemblance being their 

 sole protection, and ensuring their escape. 



We will now examine a few of the special cases in which larvas 

 resemble their food-plant so closely that they can only with difficulty 

 be detected when at rest, and, for this purpose, almost any Geometrid, 

 and numberless other, larvae offer excellent illustrations. The young 

 larvae of lodis vemaria hatches in July or August, is green in colour, 

 rests on the stems of the food-plant (Clematis), stretching straight up, 

 holding on merely by the hind claspers. It has a bifurcate hump on 

 the pro-thorax, standing forward over the head, and its resemblance 

 to a broken leaf-stalk, or tendril, is most remarkable. It is a hyber- 

 nating larva, and in the late autumn, when the leaves and stems of the 

 Clematis turn brown, the larva moults, turns brown with them, and exactly 

 assimilates in colour with the stems of the plant. This brown hue it 

 retains until the spring, and then, when it commences to feed, the brown 

 skin is discarded with the first moult, and it becomes green again like the 

 growing plant, retaining the' green colour until pupation takes place. 

 (The pupa, in a cocoon among the leaves, is also green, and the moth 

 is green). If disturbed, the larva drops by a thread, remaining quite 

 rigid, and looks just like a tiny piece of stick. 



Somewhat similar to the changes occurring in the larva of 7. ver- 

 naria are those of Geometra papilionaria. In this species, the young 

 larva, which rests chiefly on the branches of alder and birch, is of a 

 pale-brown colour, with, according to Poulton, some power of colour 

 adjustment to the twigs of its food-plant. The larva? remain brown 

 during the winter, but, in spring, moulting produces dimorphism in 

 them, some individuals becoming green, whilst others retain their 



