THE GKAPE-LEAF SKELETON IZEli. 85 



SEASONAL HISTORY. 

 NUMHEH OF (iEXEKATIONS. 



Former writers have generally attributed two generations and 

 a partial third to this insect; in fact, all, with the exception of Neal. 

 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 full gen- 

 erations in the vicinity of Washington, I). 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, 1008, and also a few very 

 young larva\ By June 30 some larva^ were almost fully grown, but 

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

 although a number of i)upa' from the early-developing larva^ were 

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

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

 growth at the latest date. 



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

 larva*, appeared continuously from July 18 to xVugust 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 pupae and did not emerge as moths, thus showing clearly 

 that there Avas not a full second generation. 



Eggs from the second-generation moths were most numerous from 

 July 20 to 23, with many second-generation larvae appearing on July 

 27. Some of the second-generation larva* wore full-grown on August 

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

 when all had gone into cocoons. 



LIFE CYCLE. 



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

 the average lengths of i^gg stage, larval period, time spent in cocoon, 

 and life of moth. The average length of the Qgg stage was 7.02 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 00.72 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 averages were taken from a very large series under 

 observation. While 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 u 



