LEPIDOPTERA. 1 67 



and divided into many distinct parts by horny, fistulous threads, more 

 or less ramified, which seem intended to support the two membranes 

 mentioned above, and which branch out from the base to the edge 

 of the wing. Their number, counting from the exterior edge, is not 

 always the same in the upper and lower wings. It varies from eight 

 to twelve. 



With its large and light wings, the butterfly can fly for a long 

 time. But this flight is not in the least regular ; it is not made in a 

 straight line. When the insect has to go some distance, it flies 

 alternately up and down. The line it takes is composed of an 

 infinity of zig-zags, going up and down, and from right to left. This 

 irregularity of flight saves the little insect from falling a prey to birds. 

 " I saw one day with pleasure," says Reaumur, " a sparrow which 

 pursued in the air a butterfly for nearly ten minuses without being 

 able to catch it. The flight of the bird was nevertheless considerably 

 more rapid than that of the butterfly, but the butterfly was always 

 higher or lower than the place to which the bird flew, and where it 

 thought it would catch it." 



But let us leave the wings to pass on to the other parts of the 

 butterfly. These other parts are the thorax or chest, the body or 

 abdomen, and the head. 



The thorax is solidly put together, so as to bear the movements 

 of the wings and legs. These latter are composed, as in other insects, 

 of five parts : the coxa, the trochanter, the thigh, the shank, and the 

 tarsus. 



Many butterflies have all their six legs of equal length. In 



Fig. 135. Leg of Butterfly armed with hooks. Fig. 136. Leg not suitable for walking. 



others, the two fore legs are very small, and are not suited for 

 walking. In others, again, they are rudimentary, being deprived of 

 hooks, very hairy, and applied on to the front of the breast. 



This difference of structure may be seen in Figs. 135 and 136, 

 one of which represents, after Reaumur, a leg unsuited for walking, 

 very hairy, and terminated in a sort of brush resembling the tail on a 

 tippet ; and the other a leg furnished with hooks. 



