84 BRITISH LEPIDOPTERA. 



specially-defended larva, e.g., A. radcliffei which mimics Datana, and 

 A. luteicoma which probably mimics Notolophus (Orgyia). 



Probably the majority of lepidopterous larvae are more or less pro- 

 tected by their general resemblance to their environment, even when 

 the protection is enhanced by the more or less exact resemblance of 

 a particular species to some special object. 



In the preceding paragraphs we have once or twice incidentally re- 

 ferred to the fact that a peculiarity of larval shape, of movement, or of 

 resting position, may constitute an efficient aid to the protection 

 afforded by some particular shade or shades of colour. Poulton (Trans. 

 Ent. Soc. Lond., 1885) discusses the protective value of the peculiar 

 attitudes assumed by the larva of Selenia bilunaria (illunaria), and the 

 peculiar rhythmical lateral movements which are observable in this 

 and other Geometrid larvae. Even the readiness of certain larvae to 

 drop to the ground when disturbed, and to remain there for a con- 

 siderable time motionless and rigid, is highly protective, and amongst 

 loose pieces of stick, pine-needles, or tall grass, a successful search is 

 almost out of the question. Poulton further observes (Ibid., 1887, 

 p. 291) that the young brown larvae of Selenia lunaria twist themselves 

 into an irregular spiral when seated on the leaves of their food-plant, 

 and that this attitude is sometimes assumed by the mature 

 larva when resting in such a position. Somewhat similar habits 

 have been noticed in the larvae of Zonosoma pendularia, Z. an- 

 nulate (omicronaria), Z. orbicidaria, Aspilates ochrearia, and A. 

 gilvaria. The young larvae of Eumia luteolata have the same habit, 

 generally sitting on the edge of a leaf, close to the place from which a 

 piece has been eaten. In this position, the larva suggests most 

 strongly the appearance of a small part of the leaf which has been 

 injured, and then curled up and turned brown, but still remains ad- 

 herent by one end to the uninjured part of the leaf. Miss Gould has 

 noticed that the brown larvae of this species have a habit of hanging 

 by a thread, twisting round rapidly whenever disturbed, and mentions 

 their similarity to bits of dead stick or pieces of leaf that one frequently 

 sees spinning in this manner. 



In most cases in which larvae resemble twigs when at rest, the 

 larva spins a slight silken pad or a few strands of silk on the branch at 

 that point where it takes up a resting position. This, of course, 

 gives it a better hold, and, in the case of Geometrid larvae, allows 

 them, after having obtained a firm grip by means of their prolegs, 

 to extend the body rigidly from the twig. The larva of A. betularia 

 and other species often, however, extend themselves obliquely between 

 two twigs, holding one by its prolegs, the other by its true legs. 

 Such a larva presents the appearance of a twig passing obliquely 

 between two others. Sometimes larvae of this description are sup- 

 ported by holding with their thoracic legs, a leaf upon, or an advanced 

 part of, the same stem as that to which they are clinging by their prolegs. 

 In this manner they are still more effectually concealed. 



The resemblance of such larvae as are effectively protected when 

 resting on twigs, to the twigs upon which they rest, is sometimes 

 greatly increased by the development of small, fleshy tubercles, "or 

 lateral hairs, along those edges of the body which are in contact with the 

 twig, and which help to break the otherwise sharp distinction between 

 the larval form and the twig. Meldola has pointed out developments 



