48 ASSOCIATION OF ECONOMIC ENTOMOLOGISTS. 



brood which had evidently just molted twice when it came nnder 

 my observation molted again after 12 days. The observations just 

 noted indicate 12 to 15 days as the interval between molting. 

 Allowing five molts per season, this gives us about 2 months for 

 a worm to mature, which is about the time required at Cedar Point. 

 Mature worms average 18.75 to 25 mm. in length (0.75 to 1 inch). 

 At the rate of growth above indicated (C.25 mm. in 22 days) Ave 

 again get about 2 months for a worm to mature. 



Judging from the number of loose heads and headless skins in the 

 nests, I conclude that the head molts first, and that the worm then 

 slips out of the old skin by this opening. I do not recall finding 

 an empty skin with a head. In only a few instances do I recall 

 that the thorax had a small, longitudinal slit dorsally. The last 

 molt occurs after the cocoon — a loose flimsy affair consisting mainly 

 of the hairs of the caterpillar with but little silk — has been formed 

 and lies stored away at the posterior end of the pupa. 



In some specimens about to molt, and which I dissected, I found 

 the digestive tract empty and the new hairs formed beneath the old 

 skin. 



OTHER OBSERVATIONS. 



It has already been remarked that a brood may divide into two 

 broods, and that two broods may unite. Again, a brood may desert 

 its old web and form a new one. I frequently noticed that many 

 webs contained worms of several different sizes, and this fact first 

 suggested to me that two or possibly several broods might unite in 

 a single web. I found later that a brood of smaller worms, somewhat 

 isolated at the end of a branch, traveled 18 inches along a bare 

 stem to reach green leaves. Every inch of this distance Avas covered 

 with quite a dense web of silk. This brood came into close prox- 

 imity with an older brood, and instead of returning to its own 

 web took up its abode in the web of the older worms. This is a 

 perfect illustration of the union of two broods. A similar occur- 

 rence Avas observed with another larger brood, Avhicli finally had to 

 travel seA^eral feet to get to its feeding leaA^es. This brood eventu- 

 ally divided, one division taking up its abode Avithin the Aveb of 

 another brood near by, while the second division built a ncAv Aveb of 

 its oAvn. It appears that the Avorms found it more convenient in this 

 case to take quarters Avith their near neighbor, or to build a neAv web, 

 than to return to their old nest. This observation illustrates both 

 the union and the division of broods, as Avell as the building of a 

 new nest. 



The following observations in a measure also illustrate some of the 

 above points, besides several others in AvebAvorm economy : I cut out 



