LEPIDOPTERA. 305 



thread-like, and not feathered. It expands from nearly one inch 

 to one inch and a quarter. 



There is a kind of caterpillar, found in July and August on the 

 balsam poplar, and sometimes on other poplars and willows, 

 whose form, posture, and motions are so odd as at once to arrest 

 attention. Its body is naked, short, and thick, tapers behind and 

 ends with a forked kind of tail, which is held upwards at an ob- 

 tuse angle with the rest of the body. This forked tail, which 

 takes the place of the hindmost pair of legs, the others being 

 only fourteen in number, is not used with the latter in creeping, 

 and consists of two movable hollow tubes, within each of which 

 is concealed a long orange-colored thread that the insect can 

 push out and draw in at pleasure. The feet are short and small ; 

 the head is small, of a purple color, and can be drawn under 

 the front part of the first ring ; the body is green, with a trian- 

 gular purple spot on the top of the forepart, and a large diamond- 

 shaped patch, of the same color, covering the back and middle of 

 the sides like a mantle, and prolonged behind to the tail. When 

 young, these caterpillars have, on the top of the first ring, two 

 little prickly warts, which disappear after one or two changes of 

 the skin. When teazed by being touched or irritated by flies, the 

 caterpillar runs out the threads from its forked tail, which it jerks 

 forwards so as to lash the sides of its body and whip off the in- 

 truder. When fully grown, it measures sometimes an inch and a 

 half in length, without including the terminal fork. Caterpillars 

 of this kind are called Cerura, horned-tail, by some, and Dicran- 

 ura, forked-tail, by other naturalists. Early in August the one 

 above described makes a tough cocoon of bits of wood and bark 

 glued together with a sticky matter, and fastened to the side of 

 a branch, the lower side beting flat and the upper convex. The 

 last transformation occurs about the middle of June, when, after 

 the end of the cocoon has been softened by a liquid thrown out 

 by the insect within, the moth forces its way through. This in- 

 sect has been figured in Mr. Abbot's work,* where it is called 

 furcula, a name, however, which belongs to an European insect. 

 It is also represented in Guerin's " Iconographie " ancfin Griffith's 



* " [nsects of Georgia," p. 141. pi. 71. 

 39 



