38 MAINE AGRICULTURAL EXPERIMENT STATION. 



APHID INVESTIGATIONS. 



In the report for 191 2 a general statement oi the purpose 

 and significance was given of 'our aphid investigations which 

 have been under way for several years. The discovery there 

 recorded of the annual migration of the woolly aphid of the 

 apple from the elm leaf to apple and the resulting knowledge 

 that the elm generations are an essential part of the life cycle 

 of this insect put a new significance upon the economic status 

 of the elm aphids and incited the entomologist of the Station 

 to concentrate attention during the past season chiefly upon the 

 woolly aphids of the elm and two bulletins just issued (No. 217 

 and No. 220) give the results of this investigation. As a brief 

 summary of the case it may be stated that in New England 

 there are five distinct though closely allied species on the elm. 

 Of these, the most important to us as an orchard state is the 

 species previously discussed which migrates to the apple from 

 the leaves of the American elm. A second species common 0.1 

 the English elm in Maine, and probably introduced into this 

 country with the tree, is a leaf curling aphid which migrates 

 to the roots of currant and gooseberry where it is a serious 

 pest. We do not yet know the full life cycle of the third 

 species, which deserts the curled leaf of the American elm in 

 the spring to pass its summer in some place still remaining to 

 be discovered. The fourth species forms a large gall something 

 the size and shape of a fig on the elm twig in the spring, but 

 we do not know its summer haunts. The fifth species appar- 

 ently confines itself to the elm alone where it is common, es- 

 pecially on young trees, in woolly clusters on the bark. 



A key is given here to aid in distinguishing the woolly aphid 

 of the apple from the other elm species with which it may 

 easily be confused in the spring of the year. 



A, Conspicuous woolly colonies on bark of Ulmus 



americana. Throughout the summer on young 

 elms. No alternate host known. Widely dis- 

 tributed in America S. rileyi 



A A. Spring generations in elm leaves, causing various 

 types of deformation. 



B. Large baggy gall on Ulmus campestris. Alternate 



host unknown. European species. Taken in Con- 

 necticut in 1913 S. lanuginosa 



