1064 



WALTER H. WELLHOUSE 



trees. During the summer of 1919 the writer saw a small Crataegus prui- 

 nosa tree killed and a very large C. punctata tree almost entirely defo- 

 liated due to the sucking of sap by myriads of these aphids. They are 

 rather large, yellowish green aphids, with long cornicles, and their most 

 easily recognizable character is the presence of four dark green spots 

 arranged in a rectangle on the dorsal side of the abdomen (fig. 108). The 

 entire life history is passed on Crataegus trees. The black winter eggs 

 are placed on the twigs and the smaller branches. They begin to hatch 

 in May, after the leaves are well opened. The young aphids move to the 

 lower surface of the leaves, and their feeding, as the colony increases, causes 

 the leaves to curl downward. 



In late June an alate brood appears and migrates to near-by branches 

 or trees to start new colonies. It is after this brood appears that the species 

 becomes so injurious. 



crataegifoliae Fitch, Aphis 



In early May, 1918, the Crataegus cocdnea trees at Ithaca began to show 

 the terminal rosettes of curled leaves caused by Aphis crataegifoliae. The 

 rosettes turned red, and the aphids within them also were red. The infested 



branches remained de- 

 formed and somewhat 

 stunted throughout the 

 season, although the 

 aphids departed from the 

 trees about May 20 to 

 seek leguminous hosts. 

 No aphids of this species 

 were observed the next 

 year. 



lanigera Hausm., Erio- 

 scma (Woolly aphis) 



The woolly aphids first 

 become noticeable in 

 early June as small white 

 spots on the tender twigs 

 of Crataegus. In a favor- 

 able season such as the 

 summer of 1918, they be- 

 come very conspicuous 

 and cover entire branches 

 by late summer fig. 109). 

 The writer has not found 

 the roots of Crataegus 



FlO. 109. ERIOSOMA LANIGERA ON HAWTHORN 



