INTRODUCTION. 71 



by a small hole, through which issues the silken thread 

 which serves so many important purposes in the re- 

 markable changes these creatures undergo. This 

 organ has been named the spinneret. On each side 

 of the under lip, and connected with it at the base, 

 are two minute palpiform bodies (e, e) 9 which may 

 be regarded as the labial palpi. 



The efficiency of the organs just described, is well 

 evinced by the address and rapidity with which these 

 creatures consume the leaves which they select for 

 their food. They invariably begin to gnaw the margin 

 of the leaf, placing the body in such a position that 

 a portion of the edge passes between the anterior 

 legs, which support and keep it steady. Before ap- 

 plying its mouth, the caterpillar stretches its body, 

 and advances its head as far as possible, that it may 

 command a larger extent of the leaf, The mandibles 

 are moved with great rapidity, and every time they 

 meet cut off a small piece, which is instantly swal- 

 lowed. At every motion of the jaws, the head is 

 drawn nearer the legs, and after it has been brought 

 as far as possible, the body being contracted for the 

 purpose, it is again extended to the point where it 

 commenced to gnaw, and the same process repeated. 

 In this manner the mandibles describe a succession 

 of arcs, and the leaf is cut in the segment of a circle, 

 somewhat resembling the circular incision made by 

 the leaf-cutting bees. It seems, also, that the notch 

 in the middle of the upper lip, formerly alluded to, 

 is of great service, as it is placed on a line with the 



