THE STATE ENTOMOLOGIST. GU 



When young they are invariably bluish-white, but when full- 

 grown they may be found either of a pale cream-color, yellow, light 

 brown or very dark brown, the different colors often appearing in the 

 same brood of worms, as I have proved by experiment, Yellow is the 

 most common color, and in all the varieties the venter is dark, and 

 there is a characteristic longitudinal black line, more or less inter- 

 rupted, along each side of the body, and a transverse line of the same 

 color (sometimes faint) between each of the joints: the head and 

 feet are ochre-yellow, and the hairs spring from dark yellow warts, of 

 which there are 10 on each joint, those on joint 1 being scarcely dis- 

 tinguishable, and those on joint 12 coalescing. There are two broods 

 of these worms each year, the broods intermixing, and the last pass- 

 ing the winter in the chrysalis state. The chrysalis (Fig. 28, b) is 

 formed in a trivial cocoon, constructed almost entirely of the cater- 

 pillar's hairs, which, though held in position by a few very fine silken 

 threads, are fastened together mainly by tiie interlocking of their 

 minute barbs, and the manner in which the caterpillar interweaves 

 them. 



The moth makes its appearance as early as the first of May in the 

 latitude of St. Louis, but may often be found much earlier in stove- 

 warmed rooms. It is easily recognized by its pure white color, by its 

 abdomen being orange above, with three rows of black spots, and by 

 the black dots on its wings. These dots vary in number, there being 

 usually two on each of the front and three on each of the hind wings, 

 though sometimes they are all more or less obsolete, except that on 

 the disk of the front wings. 



It is fortunate for us that this caterpillar is attacked by a large 

 number of insect parasites; for, were this not the case, it would soon 

 multiply to such a degree as to be beyond our control. I know of no 

 less than five distinct parasites which attack it — some living singly in 

 the body of the caterpillar, and issuing from the chrysalis without 

 spinning any cocoon of their own; others living singly in the body, 

 but forming a cocoon of their own inside the chrysalis of their vic- 

 tim, and still others infesting the caterpillar in great numbers, and 

 completely filling the chrysalis with their pupge.* 



The best time to destroy these worms is soon after they hatch 

 from their little round yellow eggs, which are deposited in clusters; 

 for, as already intimated, they then feed together. 



* For the beneSt of the scientific reader I enumerate the five parasites whieh I have ascer- 

 tained to infest this caterpillar: 1. AnonialonJIaincome (Brulle Hym IV, p. 171). 2. Ichneu- 

 mon subcganeus, Cress. {Proc. Ent. Soc, Phila., III. p. 148), and Ich. pull al us, Cress. (Pro. E. S. 

 P.. Ill, p. 145), described as a distinct species, batpullatus is evidently the male, and subcyaneus the 

 female of the same species, as I have bred from Spilosoma virginica three males all answering to 

 the description of the former, and two females both answering- to the description of the lattei 

 Ichneumon signntipes, Cress. (Trans. Amer. Ent. Soc,, I, p. 308). 4. O/jhion bilineatus, Say. (Ent. 

 of X. A., I, p. 379). 5. A small undetermined, and probably undescribed Dipteron belonging to 

 the Muscavjs. 



