ELM LEAF CURL AND WOOLLY APPLE APHID. 



239 



as an indication of the probable existence of the lice on the 

 roots. A badly attacked tree assumes a sickly appearance and 

 does not make satisfactory growth, and the leaves become dull 

 and yellowish, and even if not killed outright it is so weakened 

 that it becomes especially subject to the attacks of borers and 

 other insect enemies. 



The common forms 'both on the roots and above ground are 

 wingless lice, not exceeding one-tenth of an inch in length, of a 

 reddish-brown color, and abundantly covered, especially in those 

 above ground, with a flocculent waxy secretion. (Fig. 441.) 



In autumn, among the wingless ones, winged females, Fig. 

 440, appear in abundance. They are little, clear-winged, gnat- 





Fig. 440. Fig. 441. 



Woolly Aphid. Winged and wingless forms. Greatly enlarged. 

 (From Marlatt.) 



like objects, greenish-brown, almost 'black in color, with the 

 body covered with more or less of the cottony secretion. These 

 are the fall or return migrants that seek the elm bark to give 

 birth to the generation of true sexes, minute wingless, beak- 

 less creatures, the female of which deposits a single "winter 

 egg" within a crevice of the elm bark. 



On the elm the stem mother, which hatches from the over- 

 wintering eggs sheltered in rough crevices of the bark, appears 

 early in the spring and may be found in Maine before the mid- 

 dle of May stationed on the partly opened leaf buds. 



By the last of May the earliest of these wingless stem mothers 

 (Fig. 443) are mature and found in the leaf curl (Fig. 442) or 



