ELM LEAF ROSETTK AND WOOLLY APHID OF APPLE. 33! 



of a reddish-brown color, and abundantly covered, especially in 

 those above ground, with a flocculent waxy secretion. Fig. 63 



In August and later, among the wingless ones, winged females 

 appear in abundance. Fig. 62. They are little, clear-winged 

 aphids which look nearly black unless carefully examined when 

 the abdomen is found to be dark yellowish red or rusty brown. 

 These are the fall migrants that leave the apple and seek the 

 elm before giving birth to the generation of true sexes, minute, 

 wingless, beakless creatures, the female of which deposits a 

 single "winter egg" within a crevice of the elm bark. 



The flight of the fall migrants away from the apple is appar- 

 ently a common observation of all who have studied this species 

 either in this country or abroad,* but it is only recently that the 

 significance of this flight has been appreciated, it having been 

 thought previously to be merely a dispersal from one apple tree 

 to another. 



Where woolly aphid colonies are very thick, the true sexes 

 and the winter eggs are sometimes found upon the apple tree. 

 That such occurrences are accidental seems probable as fall 

 migrants of most species will occasionally dispose of their pro- 

 geny before reaching the appropriate winter host. 



A record of such an occurrence is to be found in the Report of the 

 Entomologist of the United States Department of Agriculture for the 

 year 1879 by J. Henry Comstock. On page 259 of this Report, Dr. 

 L. O. Howard recorded his observations made in a little orchard of 

 Russian apple trees then on the grounds of the Department of Agricul- 

 ture at Washington, his statement concerning the winter egg being as 

 follows : 



"The winter egg was found on several occasions during the winter 

 in crevices of the bark over which a colony had been stationed during 

 the summer. It was a rather long ovoid, measuring .322 mm. (.125 inch) 

 in length and was very similar to the winter egg of Colopha ulmicola 

 (Fitch), as described by Riley in Bulletin No. i, Vol. V, Hayden's 

 Survey. 



"This egg was laid, as Professor Thomas supposes, by a wingless 

 female, differing from the ordinary agamic form to a certain extent. 

 These females we only know from finding their skins around the winter 

 egg, since they often die without depositing it. The males we have not 



*Dr. O. Schneider-Orelli records also the development of winged 

 forms in June. 



Sonderabdruck aus Heft 7/8 des XII. Bandes der Mitteilungen der 

 Schweizerischen Entowologischen Gesellschaft. 1915. 



