THE GRAPE-LEAF SKELETONIZER. 85 



SEASONAL HISTORY. 

 NUMBEH OF (JEXEKATIONS. 



Former writers have generally attributed two generations and 

 a partial third to this insect; in fact, all, Avith the exception of Xeal. 

 who states that there are three broods in Florida, are of the opinion 

 that there are two broods. Extended observations and studies dur- 

 ing the past summer reveal the fact that there are not two fidl gen- 

 erations in the vicinity of Washington, D. C. Seasonal history 

 studies show that moths from the over-wintering pupa^ appear dur- 

 ing the latter part of May or chiefly during the first ten days of June. 

 Eggs from these moths were found June 11, 1908, and also a few very 

 young larva\ By June 80 some larvne were almost fully grown, but 

 the majority of full-grown larva^ did not appear nntil about July 14, 

 although a number of pupa? from the earl\'-developing larviv were 

 fouiul on July 7, showing a long period from the appearance of the 

 first full-grown larvte to the appearance of those which attained their 

 growth at the latest date. 



The second generation of moths, or those from first-generation 

 larvae, appeared continuousl}- from JuW 18 to August 15, giving a 

 very extended period of emergence and accounting for the tendency of 

 former writers to attribute the late-appearing ones to a third genera- 

 tion. 



The largest number of moths appeared from July 20 to 25. A 

 number of those larva^ which had attained their growth by July 14 

 hibernated as pupa? and did not emerge as moths, thus showing clearly 

 that there was not a full second generation. 



Eggs from the second-generation moths were most numerous from 

 July 20 to 23. with many second-generation larva^ appearing on July 

 27. Some of the second-generation larva^ Avere full-grown on August 

 24 and were spinning cocoons on that date and up to September 16, 

 when all had gone into cocoons. 



LIFE ( yCLE. 



The average length of the life cycle was found by adding together 

 the average lengths of egg stage, lar\al period, time sjDent in cocoon, 

 and life of moth. The average length of the e<rg: stage was 7.92 days, 

 the average length of the larval period 40.5 days, the average time 

 spent in cocoon 14.8 days, and the average length of life of a moth 

 3.5 days; thus, the average length of the complete life cycle was found 

 to be GG.72 days. The minimum life cycle, found by taking the mini- 

 mums of the various periods and adding them together, was 53 days. 



All of these aAerages were taken from a very large series under 

 observation. AAliile the above figures should not be taken and used 

 to find how many generations there are in any given locality, they 

 will give some clue to the time required for the development of a 



