118 FOURTH ANNUAL REPORT OP 



til black. At this stage a mealy powder begins to manifest itself on the surface of the body. After 

 the 3rd moult it is of a still paler cream-color, and only the stem of the stigmtital tubercles remains 

 Ijlack, the knob and bristles being cream-colored: the head, leg.s, and anus are now sulphur-yellow; 

 the stigmata are larger, and there are two black spots at base of prolegs and three at base of tlioracic 

 legs, the central one elevated and forming, as it were, a spine. (These spots are often visible after 

 the second moult.) The white powder-like or wax-like secretion, now covers the body giving it a 

 most delicate look. After the last moult the tubercles become blue— the lower row having black at 

 hase— and as the worm approaches its full growth, the white powder for the most part gets 

 rubbed off and vanishes. When full grown it appears as in the upper part of Figure 42 and is of a 

 light mealy bluish-green, freckled— aside from the black or, as they now often appear, blue-black 

 spots already mentioned — wiih numerous roundish spots of a darker green, more decided laterally 

 and ventrally : the head and thoracic legs are shiny yellowish-green, and the ()rolegs and anal joint 

 pale orange-yellow. 



Within a month after hatching the worm spins up, forming its cocoon 

 (Fig. 2, 3) within the leaf which is drawn partly around it, and fastening the 

 leaf stalklet to the main stalk with strong silk. In five diiys it becomes a 

 ■c-hrysalis (Fig. 2, 4) and, if of the first brood, produces the jnoth within three 

 weeks afterwards. The second brood of worms generally have the instinct 

 to fasten their Cocoons to the more permanent twigs, to which tliey hang 

 securely during the winter; but they often attach them to the leaf stalk, 

 with which they are carried to the ground in the fall ; and the streets of the 

 cities in which the}^ have become wild are often strewn with such cocoons 

 which get trodden on and ruined. 



The moth (Fig. 42, ,2, $ ) is of a rusty yellow color inclining to green 

 <ind marked with pale lilac and white with transparent crescent spots as in the 

 illustration. The males are smaller than the females, having smaller bodies 

 and narrower wings, the hind ones, especially, being much less rounded. 

 The maleantennfe are scarcely an}- broader than those of the female. 



The above descriptions are general in their character. The insect is 

 not only variable in intensity of markings and coloration; but likewise, to 

 an unusual degree, in the time required for development. Some of the first 

 ones I bred were very irregular in this respect, part of the second brood is- 

 suing as moths in the flxll, and part remaining over winter in the cocoon till 

 the middle of the following June. I have also had the chrysalis remain not 

 only through one winter, but throughout the summer and succeeding sec- 

 ond winter, and not give forth the moth till the second summer; though 

 the cocoons were submitted to precisely the same conditions under which 

 others, hatched from the same batch of eggs, issued in the fall of the year in 

 which they were hatched. This is the common experience of most persons 

 who have raised the woi-ms in large quantities. 



A high temj)erature generally hastens their development, as it does in 

 other insects; and while my summer broods averaged but 25 days from the 

 time of hatching to spinning, those of the fall brood which issued the same 

 year, averaged 30. 



Some specimens w^hich I happened to have feeding in 1869 in cages 

 contiiining plum twigs as well as ailanthus, seemed to eat the leaves of the 

 former with as much relish as of the latter; and no doubt other food-plants 

 might be found for this insect, if it were desirable. In Europe they have 

 also been fed with success on Rhus coriaria and Pimpernel; while Dr. Wal- 

 lace has fed them with Plum and Laburnum producing moths weakened and 



