A FURTHER CONTRIBUTION TO THE STUDY OF ERIO- 

 SOMA PYRICOLA, THE WOOLLY PEAR APHIS 



By A. C. Baker, Entomological Assistant, and W. M. Davidson, Scientific Assist- 

 ant, Deciduoiis Fruit Insect Investigations, Bureau of Entomology 



In the present paper, in which the complete life cycle of Eriosoma 



pyricola is given, it seems best to discuss somewhat fully the history of 



the different species recorded on pear roots (Pyrus communis). This 



is especially urgent since complete life studies of the woolly pear aphis 



have shown that the spring forms as present on elms are remarkably 



different from the fall forms upon pear roots; in fact, one of the chief 



characters used in the separation of the species does not exist in the 



spring forms at all. This is remarkable in view of the fact that this 



same character, the wax pores, has been the chief one in linking the 



different forms of other species closely related to the root aphis of the 



pear. 



SYSTEMATIC DISCUSSION 



In 1849 Westwood (10)* described and figured the work of an aphid 

 on Nelis d'Hiver pear. This injury consisted of knotty growths and 

 swellings on the branches very similar to those produced by the woolly 

 apple aphis, Eriosoma lanigerum, (Hausmann). A short description 

 and figures of the insect were given with the statement that the species 

 "may be called Eriosoma pyri." The woolly apple aphis is known com- 

 monly to affect pear trees above ground, while the woolly pear aphis is 

 met only upon the roots. It seems extremely probable, therefore, that 

 the form described by Westwood was none other than the common 

 woolly apple aphis. This, however, the writers have been unable to 

 prove definitely. 



In 1 85 1 Fitch (4) described an aphid from apple roots under the name 

 "Eriosoma pyri." The author stated that this species formed galls 

 upon the roots. Since the work which Fitch credited to his E. pyri was 

 very similar to that of the woolly apple aphis, if indeed not the work of 

 that species, Fitch's E. pyri was later considered to be the same as E. 

 lanigerum (Hausmann). A large aphid, a species of Prociphilus, occurs 

 upon the apple in the Eastern States, and is not uncommonly found 

 upon the pear, the fall migrants and sexes being usually seen upon those 

 trees. The senior writer (i) has shown, from an examination of Fitch's 

 types, that this form is the one described by Fitch as E. pyri. In this 

 paper by the senior writer the species is redescribed as Prociphilus pyri 

 (Fitch). The description of the earlier form by Westwood (10), how- 



1 Reference is made by number to "Literature cited," pp. 73-74- 



Journal of Agricultural Research, Vol. X, No. 2 



Washington, D. C. July 9, 191 7 



is Key No. K— 54 



(65) 



