412 



LEPIDOPTERA 



pennaria is said to have in early life a pair of imperfect feet on 

 the eighth segment, which disappear as the larva approaches 

 maturity. 



The position of the abdominal feet and claspers throws the 

 holding power of the larva to the posterior part of the body, 

 instead of to the middle, as in other caterpillars. This, com- 

 bined with the elongate form, causes these larvae when reposing 

 to assume attitudes more or less different from those of other 

 larvae ; holding on by the claspers, some of these Insects allow all 

 the anterior parts of the body to project in a twig-like manner. 

 The front parts are not, however, really free in such cases, but 

 are supported by a thread of silk extending from the mouth 

 to some point near-by. Another plan adopted is to prop the 



front part of the body 

 against a twig placed 

 at right angles to the 

 supporting leaf, so that 

 the caterpillar is in a 

 diagonal line between 

 the two (Fig. 202). 

 Other Geometers assume 

 peculiar coiled or spiral 

 attitudes during a whole 

 or a portion of then- 

 lives ; some doing this 

 on a supporting object 

 leaf or twig while 

 others hang down 

 ( EI>!I yra pendularia). 

 Certain of the larvae of 

 Geometridae vary in 

 colour, from shades of 

 brown to green ; there 

 is much diversity in 

 this variation. In some 

 species it is simple variation : in others it is dimorphism, 

 i.e. the larvae are either brown or green. In other cases the 

 larvae are at first variable, subsequently dimorphic. In Amplii- 

 dasis betularia it would appear that when the larva is hatched 

 the dimorphism is potential, and that the future colour, whether 



FIG. 202. Larva of Amphidasis betularia, reposing 

 on a rose-twig. x 1. Cambridge. 



