74 THE EEPOET OF THE No. 36 



laboratory by Mr. J.- D. Tothill and his assistants, and is under the general 

 direction of the Dominion Entomologist, Dr. C. Gordon Hewitt. 



The insects in question are the Forest Tent Caterpillar and the Fall Webworm. 

 The object of the work has been to study the control of each insect at the same places 

 for a period of consecutive years. The work has resolved itself into a study of 

 the causes of outbreaks of these and other insects, and of the factors that in the 

 natural course of events, cause these outbreaks to subside. 



In 1911, when the study was commenced, both the Forest Tent Caterpillar and 

 the Fall Webworm were exceedingly abundant, and w^re doing great damage 

 throughout the Eastern United States and Canada. Since then they have become 

 less and less numerous and in 1915 there remained only a few local infestations 

 and practically no damage was reported. 



This story of great abundance followed by a period of scarcity is merely a 

 repetition of a story that has been told and retold many times in the past history 

 of this continent. It is the purpose of this paper to give an historical account of 

 these two insects as gleaned from the records of the White Man written during 

 Jiis few centuries of residence in this land. 



For the purposes of this account it has been found convenient to divide the 

 continent into three regions. On the map (p. 73) these are indicated, the Eastern 

 and Western being marked with parallel lines and the Central occupying the 

 intervening territory. The Eegions are treated separately. The accounts of these 

 insects are much more complete and siatisfactory for the Eastern Eegion than for 

 either of the others. A glance at the charts (pp. 76, 81) will show to what extent 

 the abundance of the insects has been uniform for the three Eegions, 



In these charts the term " local ravages " has been used to designate out- 

 breaks which are recorded as occurring only in smaller sections of the main 

 divisions, or Eegions. As will be noticed these outbreaks occurred largely previous 

 to 1860, and there are at least two explanations for their seemingly local dis- 

 tribution: (1) The limited number of observers recording such data prior to that 

 time and (2) The more or less limited food supply of the insects. It seems 

 quite probable that the food plants of both species, but especially of the Forest 

 Tent Caterpillar have greatly increased with the spread of civilization. This 

 question is, however, too many-sided to permit of a full discussion here and will be 

 left for another paper, dealing with this su1)ject, which it is hoped will be published 

 from the lal)oratory at a later date. 



The author wishes to take this opportunity of thanking Dr. C. J. S. Bethune, 

 Professor of EntomSlogy at Guelph, for his kindly assistance in connection with 

 the library work at Guelph. He also wishes to thank Mr. Tothill for his many 

 helpful suggestions and kindly criticisms. 



FoEEST Tent Cateepillae. 

 Eastern Region. 



The original habitat of the Forest Tent Caterpillar in North America seems 

 to have been in the Eastern Eegion, for it is here that we find its ravages first 

 recorded. ■ 



The first authentic record of the presence of the Forest Tent Caterpillar is 

 that compiled from earlier observations by Mr. Abbot and published by Sir J. E. 

 Smith in 1797 in his ' Lepidopterous Insects of Georgia.' He gives good colored 

 figures of the larva and imago, and states that " This kind is sometimes so plenti- 



