26 THE BUTTERFLIES OF THE 



damp evening or a warm rain is more conducive to this 

 change than dry weather. 



THE IMAGO. 



After emerging from the pupa-shell the butterfly finds 

 some place, often the pupa-case, where it may rest with 

 the body hanging downward, and after a moment's delay, 

 as if for rest, it proceeds to expand the wings, which 

 were before not larger than the finger-nail. This is done 

 partly by their own weight, but mostly by forcing air 

 into the hollow veins that constitute the framework of 

 the wings. After the wings are expanded to their full 

 size, the insect remains till they are fully dry before it 

 flies away. 



A butterfly has three principal divisions of the body, — 

 the head, thorax, and abdomen. The head is more or 

 less globular, and contains the mouth parts, the eyes, and 

 the antennae as its principal divisions. On either side 

 of the head are the eyes, two convex hemispheres that 

 are made up of a great number of small eyes 

 or facets, the whole on each side of the head 

 being known as a compound eye. In some 

 species as many as three thousand six hundred 

 of a^om- an( l fifty facets have been counted in a single 

 pound e y e> Each of these is hexagonal in shape (see 

 Fig. 4), and contains all the parts of a perfect 

 eye. The surface of this compound eye may be smooth, 

 or moderately covered with short hairs, which are situ- 

 ated between the facets. Some of the moths have besides 

 the compound eyes ocelli above these, and it is said one 

 species of the butterflies has one on each side ; but aside 

 from this these insects have only the compound eyes. 



