OF THE STATE ENTOMOLOGIST. 147 



stage; the papillre are more nimierousand more uniform in size, and in some specimens 

 sub-obsolete ; the dark marking's are more often lacking, as before described, (Rep. 2, p. 

 127), but sometimes so prominent as to give the worm a brown liue. Considerable varia- 

 tion in the markings of tlie head may also be noticed in different individuals of the 

 same age. 



, Like the larva of the Archippus butterfly, it goes through but 

 three molts, and, like that larva, it furnishes an excellent illustration 

 of the fact that the head increases in size between the molts. It ma- 

 tures very rapidly, and often acquires its full growth within three 

 weeks. In suspending for the transformation to chrysalis, the body 

 is bent almost in a circle, the head being brought close to the anus ; and 

 so rapid is the transition, during hot weather, that by five o'clock p.m., 

 I have had the dry and hardened chrysalis from larvae which were not 

 suspended till 10 a. m., of the same day. During the suspension of 

 the larva, a pale transverse elevation (corresponding to that of the 

 future chrysalis) appears distinctly across the middle of joint 7, and 

 it is very patent that the head of the chrysalis is formed under the 

 head of the larva — that the pro, meso and meta-thorax correspond to 

 joints 1, 2 and 3, and that the second pair of larval spiracles is covered 

 by the hind wing-sheaths in the chrysalis, while the ninth larval pair 

 becomes obsolete and closed. 



The transverse ridge across the abdomen, and the ridges around the wing-sheaths 

 and the head, are white, with a lilaceous tint in the fresh chrysalis, and the dusky spots 

 are arranged in eight longitudinal rows, two dots to a joint. The anal clasp consists 

 of a rounded knob, densely covered with short, dark brown barbs, and connected with 

 it ventrally is a conspicuous black cordate mark. 



NEW FOOD PLANT. 



The Goat-weed occurs very sparingly in the immediate vicinity 

 of St. Louis, and not till we reach Highland, Illinois, on the'Vanda- 

 lia railroad, is it found in profusion. The butterfly is, nevertheless, 

 quite common. Suspecting, from these facts, that it must breed on 

 some other plant, I soon discovered such to be the case. While Gro- 

 ton capitatum is rare, another species of the same genus, the Croton 

 monantJioqymim Michx., is very abundant, and especially just over 

 the river, at East St. Louis. This plant is rather more woody, grows a 

 little lower, and has a much smaller, deeper green leaf than cainta- 

 tum; and, though separated from Croton by some botanists, and 

 called Engelmannia by one of them. Dr. Engelmann himself consid- 

 ers it a good enough Croton. 



Unless very well grown on rich soil, several leaves are necessary 

 to make a case, and the larva knows well how to adapt itself to the 

 ■circumstances. 



The perfect imitation of the food-plant by the larva is remarkable, 

 for those found on capitatum are generally paler than those on mo7i- 

 antliogynum. It is upon this last plant, later in the season, that I 



