the size of their bodies are usually very large, and which are remarkable for the 

 beauty of the colors and the markings which they display both on the upper and 

 on the under side. 



The wings consist of a framework of horny tubes which are in reality double, 

 the inner tube being filled with air, the outer tube with blood. The blood of insects 

 is not, like that of vertebrates, red in color. It is almost colorless, or at most 

 slightly stained with yellow. The circulation of the blood in the outer wall of the 

 wing-tubes takes place most freely during the brief period in which the insect is 

 expanding its wings after emergence from the chrysalis, concerning which we shall 

 have more to say elsewhere. After the wings of the butterfly have become fully 

 expanded, the circulation of the blood in the wings ceases almost entirely. The 

 horny tubes, which compose the framework of the wings of butterflies, support 

 between them a delicate membrane, to which upon both the upper and lower sides 

 are attached the scales. The two fore wings are more or less triangular in outline; 

 the hind wings are also subtriangular, but are generally more or less rounded on the 

 outer margin, and in numerous forms are provided with tails or tail-like prolonga- 

 tions. 



Inasmuch as in describing butterflies authors generally devote a good deal of 

 attention to the markings of the wings, it is important for the student to become 

 acquainted with the terms employed in designating the different parts of the wings 



