THE AMERICAN ENTOMOLOGIST. 



57 



the tree upon which it feeds, — which tree 

 is known to flourish on all kinds of soil 

 and in widely different latitudes. 



There are some interesting features in 

 the natural history of this worm. The 

 female deposits on an average, two hundred 

 and fifty eggs.* These are about 1.6'°°'. 

 long, oval in form, and of a cream color 

 (Fig. 16, a). They are spotted in places 

 with dark green or black particles, which 

 can be rubbed off and which under the 

 microscope are found to consist principally 

 of gum, mixed with minute hairs. 



The moth fastens them by means of a gum 

 with tolerable firmness to whatever object 

 she may be upon. They are however easily 

 detached, and if subsequently placed on 

 moist cloth or paper will again adhere. 

 They hatch at a temperature of 65° Fahr. 



Within a month after hatching the worm 

 (Fig. 16, 3) spins up, forming its cocoon 

 (Fig. 16, c) within the leaf which is drawn 

 partly around it, and fastening the leaf 

 stalklet to the main stalk with strong silk, 

 In five days it becomes a chrysalis (Fig. 1 6, d), 

 and if of the first brood, produces the moth 

 within three weeks afterwards. The second 

 brood of worms generally have the instinct 

 to fasten their cocoons to the more perma- 

 nent twigs, to which they 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 they have be- 

 come wild are often strewn with such co- 

 coons which get trodden on and destroyed. 



The moth is of a rusty yellow color 

 inclining to green, and marked with pale 

 lilac and white, with transparent crescent 

 spots. The males are smaller that the 

 females, having smaller bodies and nar- 

 rower wings, the hind ones, especially, 

 being much less rounded. The male 

 antennffi are scarcely any 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 color- 

 ation, but likewise, to an unusual degree, 



* Parthenogenesis has been known to occur exceptionally 

 in this as in other species of the family. See Annates de 

 la Soc. Ent. de France. 1872. LXII. 



in the time required for development. In 

 a number of them which we have had under 

 close observation, some of the first that 

 were bred were very irregular in this re- 

 spect, part of the second brood issuing 

 as moths in the fall, and part remaining 

 over winter in the cocoon till the middle 

 of the following June. The chrysalis has 

 also remained not only through one win- 

 ter, but throughout the summer, and suc- 

 ceeding second winter, and not giving 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 ex- 

 perience of most persons who have raised 

 the worms in large quantities. 



A high temperature generally hastens 

 their development, as it does in other in- 

 sects ; and while many of those of the sum- 

 mer brood average but 25 days from the 

 time of hatching to spinning, those of the 

 fall brood which issue the same year, aver- 

 age 30 days. 



Some specimens which we happened to 

 have feeding in 1869, in cages contain- 

 ing plum twigs as well as Ailanthus, seemed 

 to eat the leaves of the former with as 

 much relish as of the latter ; and no fioubt 

 other food plants might be found for this 

 insect, if it was desirable. In Europe 

 they have also been fed with success on 

 Rhus coriaria and Pimpernel ; while Dr. 

 Alexander Wallace, of London, has fed 

 them with Plum and Laburnum, producing 

 moths weakened and defective in size. He 

 gives, in one of his papers, a vfery interest- 

 ing account of some dwarfs produced from 

 celery-fed worms. 



The silk of the Ailanthus worm is no 

 doubt very valuable, but to what extent, 

 depends on our ability to manufacture it 

 successfully. It has several disadvantages, 

 but native ingenuity may devise some 

 means to overcome them or turn them to 

 account. The value of any silkworm de- 

 pends on our ability to unwind its cocoon. 

 The cocoon of this worm is prolongated and 

 its threads are attached by strong and very 



