UNITED STATES DEPARTMENT OF AGRICULTURE 



In cooperation with the 

 Connecticut Agricultural Experiment Station 



DEPARTMENT BULLETIN No. 1238 



Washington, D. C. 



October 15, 1924 



THE CANKERWORMS. 1 



By B. A. Pobteb, Entomologist, and C. H. Alden, Scientific Assistant, Fruit 

 Insect Investigations, Bureau of Entomology. 



CONTENTS. 



Page. 



Introduction „ . 1 



Economic history 2 



Scientific history 3 



Synonymy 4 



Common names 4 



Differences between the species 5 



Food plants 5 



Distribution 6 



Fall cankerworm 6 



Spring cankerworm 6 



Means of dissemination 6 



Economic importance 8 



Fall cankerworm 9 



Descriptions 9 



Seasonal history and habits ' 11 



Page. 



Spring cankerworm 20 



Descriptions 20 



Seasonal history and habits 22 



Natural control 28 



Weather conditions 28 



Diseases 29 



Starvation 29 



Birds 29 



Insect enemies 30 



Other enemies 31 



Control measures 32 



Cultivation 32 



Spraying 32 



Mechanical barriers 33 



Summary 35 



Literature cited 36 



INTRODUCTION. 



The fall cankerworm (Alsophila pometaria Harris) and the spring 

 cankerworm (Paleacrita vernata Peck) have been known in New 

 England for more than two centuries, and in the Mississippi Valley 

 for three-quarters of a century. The studies which form the basis 

 of this bulletin were carried on at the laboratory maintained by the 

 Bureau of Entomology at Wallingford, Conn., in cooperation with 

 the Connecticut Agricultural Experiment Station at New Haven, 

 for the study of insects affecting deciduous fruit trees. With the 

 exception of one small isolated orchard which was badly infested 

 with the spring cankerworm until the owners commenced spraying, 

 neither species has been seriously abundant in the vicinity of Wal- 

 lingford the past few years, although both were present in fair 

 numbers. 



The two species have much in common, and wherever possible they 

 have been treated together. 



1 The work upon which this bulletin is based was done under the direction of Dr. A. L. 

 Quaintance. The life-history work in connection with the spring species was carried on 

 largely by the junior author ; that on the fall form, for the most part by the senior author. 



