THE CANADIAN ENTOMOLOGIST. 49 



larvae reared upon the leaves of Sambucus Canadensis, are the largest that 

 I have ever seen. They measure fully four and a half inches in length, 

 and have a diameter of nearly three inches. They are less compact than 

 those found upon any of the foregoing plants, being very light and con- 

 siderably inflated. The chrysalis within is proportionally large. In some 

 parts of the country, along the borders of thickets and waste fields, they 

 are found in abundance, and thrive handsomely upon the elder. The 

 moulting periods are shorter, and the chrysalis stage is attained at least a 

 fortnight sooner than is usual. At first, where plants more congenial to 

 the taste, are in close proximity, a disposition to stray thereto was discern- 

 ible. To obviate this difficulty, perfectly isolated plants were selected, 

 which proved highly successful. Frequent attempts to rear caterpillars 

 before the first moulting was over, upon foreign plants, proved in every 

 case an utter failure. It is doubtless true that instinct has much to do in 

 the matter, but may it not be that the jaws and legs are so constructed at 

 first as to be only adapted to cutting and holding on to the leaves of par- 

 ticular plant-species ? This being so, with the further development of 

 these organs, would certainly come the power of adaptability to take 

 advantage of the changes thus introduced into their environment. 



The food has certainly much to do with the color of the cocoon. 

 Caterpillars feeding upon the leaves of the common red currant, produce 

 silk of a deep reddish-brown color ; while the leaves of the cherry, plum, 

 and the several species of Rosa, give a light brown color, bordering on 

 gray. Cocoons taken from Spircea, Syinphoricarpiis and Primus serotina, 

 are invariably a grayish-brown. There is also plainly noticeable in 

 caterpillars feeding upon these plants, with the exception of those feeding 

 upon Ribes rubriini, a tendency to lighter colors, which in some cases is 

 decidedly marked, as in the case of those feeding upon the leaves of Pninus 

 dotnestica, where the lateral tubercles often display a beautiful pearl 

 color. 



That food has certainly much to do in determining the sexes among 

 Lepidoptera, I think has been clearly shown in the writings of Mrs. Treat, 

 and in those of the author, although leading authorities are disposed 

 to think differently. But, notwithstanding their opinions to the contrary, 

 I cannot be deterred from placing upon record my experience of the past 

 summer with Platysamia cecropia. As before remarked, quite a number 

 of caterpillars were constrained to feed upon the leaves of plants that 

 betrayed anything but a healthy appearance. It has been already shown that 



