THE BUTTERFLY. 65 



base of the latter a little outward and giving them 

 greater freedom of motion. With the thighs, or 

 femora, the principal part of the movable leg be- 

 gins [see Figs. 172-177] ; they are straight, long, 

 and slender, perfectly simple in structure and 

 clothed only with scales or hairs, the latter often 

 forming fringes along the edge ; in them lies 

 most of the muscular mass of the legs ; the tibiae 

 or shanks are also straight, but much slenderer 

 than the thighs and of about the same length ; 

 when the insect is resting or walking they are 

 usually held at about right angles with the 

 thighs ; they are always scaled, and generally 

 furnished throughout with one or two rows of 

 spines, besides a pair of longer movable spines or 

 spurs at the tip. In the lowest butterflies the 

 front tibiae bear a slender leal-like appendage 

 projecting from the middle of the inner sur- 

 face, and clothed with a velvety down [see Fig. 

 173] ; its use or purport is wholly unknown, but 

 its position reminds us of the extraordinary tym- 

 pana on the front legs of crickets and long-horned 

 grasshoppers, which are unquestionably organs 

 of hearing and occur only in those groups which 

 stridulate the loudest. The few butterflies, how- 

 ever, which are known to produce sounds belong 

 to the highest family of Lepidoptera, in which 

 this structure is totally absent ; and whatever its 

 use it is probably only a modified spur, such as 



