2 THE BUTTERFLIES OF THE BRITISH ISLES. 



who may desire information on this subject are referred to 

 Sharp's " Insects," Part L, in the " Cambridge Natural History," 

 where also will be found much interesting and instructive matter 

 connected with the caterpillar and chrysalis, to which stages 

 only brief reference can here be made. 



The Caterpillar. 



The second stage is that of the caterpillar, and in some 

 species, such as the Red Admiral, this is of very short duration, 

 a few weeks only, whilst in others, as for example the Small 

 Blue, it usually lasts for many months. There is considerable 

 diversity both in the shape and, where it is present, in the hairy 

 or spiny clothing {armature) of caterpillars. All, however, are 

 alike in one respect, that is the body is divided into thirteen 

 more or less well-defined rings (segments), which together with 

 the head make up fourteen divisions. In referring to these 

 body-rings, the first three nearest the head, each of which is 

 furnished with a pair of true legs {thoracic legs), are called the 

 thoracic segments, as they correspond to the thorax of the 

 perfect butterfly. The remaining ten rings are the abdominal 

 segments ; the last two are not always easily separable one from 

 the other, and so for all practical purposes they may be con- 

 sidered only nine in number. These nine rings, then, correspond 

 to the abdomen of the future butterfly. The third to sixth of 

 this series have each a pair of false legs {prolegs), and there is 

 also a pair on the last ring ; the latter are the anal claspers. 



The warts {tubercles) are the bases of hairs and spines, and 

 are to be seen in most butterfly caterpillars, but they generally 

 require a lens to bring them clearly into view. These warts are 

 usually arranged in two rows on the back {dorsal series) and 

 three rows on each side {lateral series). 



All the various parts referred to, or to be presently mentioned, 

 may be seen in Fig. i, which also shows a peculiarity that is 



