The Bud Moth. 41 



the mid-rib and branches out along the large veins into irregular 

 areas. (Fig. 7.) 



From the time the larvae emerged from the eggs in our cages 

 (July 11) they received careful attention. Some were placed out- 

 doors on a tree under a net; and the food in the cages was kept as 

 fresh as possible and their habits of growth an 1 feeding noted. And 

 although the observations upon their feeding habits as recorded above 

 agree in general with those of Dr. Fernald, there were no such changes 

 took place in the size and appearance of the larvje as he describes.* 



Our observations show that the greenish color of the larva when it 

 first emerges changes in a day or two to a dark brown, slightly lighter 

 than that of the mature larva; and the larva then maintains this brown 

 color throughout its whole existence . The head and thoracic shields 

 change to black, but the anal shield in the early stages of the larva is 

 scarcely to be distinguished from the body color; rarely does a mature 

 larva have the anal shield blackish. The larvae grow very slowly. 

 Instead of attaining a length of 4 mm. in a week (as did Dr. Fernald'sj, 

 they did not moult or cast their skin the first time until five days after 

 emerging. They then measured 2.25 mm. in length, and the head was 

 now but little wider than the body. The second moult occurred seven 

 days after the first. Ihere was no change in the appearance of the 

 larvae except in size, they then measuring 3 mm. in length. July 28, 

 or five days after the second moult, the larvae cast their skins for the 

 third time and attained a length of 4 mm.f 



*Dr. Fernald says : " When the young larva hatches it does not eat the shell 

 of its egg, but goes on to the tenderest leaves and almost immediately begins 

 spinning a microscopic layer of silk, under which it eats the outer layer or 

 epidermis of the leaf. The larva is then about three millimeters in length, of 

 a creamy white color, with head, thoracic and anal shields blackish brown, 

 and a few minute pale[hairs on the body; the head is very large for the rest of 

 the body. In a week the larva is nearly four millimeters long, light yellowish 

 brown, with the head, thoracic and anal shields dark brown, and it eats 

 minute holes through the leaf, its silken web now being visible to the naked 

 eye. The larva gradually becomes a trifle more brownish, increases in size 

 and enlarges its web along the side of the mid-rib." 



fit may be of interest to some to know how it was determined when the 

 larva had moulted, working as it does mostly out of sight. The method 

 employed was that used by Mr. H. G. Dyar, who has worked out the number 

 of moults of many species of caterpillars. He found that the diameters of the 

 head of a larva taken after each moult formed a geometrical series. The head 

 being chitinous does not increase in size between the moults. So that by 

 ascertaining the diameter of the head before and after a moult a ratio could be 

 taken with which the terms of the series could be obtained ; or, in other words, 

 one could calculate what the diameter of the head of the larva was going to 



