WOOLLY APHID OF THE APPLE. 179 



be a difficult problem to decide which is lanigera! The other two leaf 

 curlers, however, are certainly distinct. 



There are apparently 3 summer generations of progeny of the 

 elm leaf migrants upon the apple in Maine, — ^two apterous gen- 

 erations followed by a generation part of which, the fall mi- 

 grants, become winged and leave the apple and part develop into 

 apterous forms and remaining on the apple give birth to nymphs 

 which while still young seek protection at the base of the tree 

 for the winter and are known as the hibernating nymphs. 



It is the function of the migrants to seek the winter host 

 and there give birth to the true sexes. These are the tiny yel- 

 lowish brown egg-laying females and the still smaller pale yel- 

 low males. Both sexes are wingless and with rudimentary 

 mouth parts which are apparently functionless. One compara- 

 tively large yellow tgg occupies nearly the whole abdomen of 

 the female and with the deposition of this the cycle of the spe- 

 cies closes, — or begins. It is too complicated a p>erformance to 

 follow easily but the outline on page 182 will be useful as a 

 summary. Such a cycle with the annual migration to and from 

 the apple with the elm serving as host for the first three spring 

 generations is undoubtedly typical for lanigera. The hibernat- 

 ing nymphs which remain protected about the crown of the 

 apple over winter and ascend to tender places on the bark be- 

 fore feeding in the spring give what looks like a "closed cycle" 

 of apterous viviparous females persisting on the apple. How 

 long such a colony could maintain itself on the apple without 

 fresh material from the elm I do not know.* 



I am certain that in Maine the natural enemies of the woolly 

 aphid would cut its career short and that it wouid not assum.e 

 the status of a pest of consequence if it did not shift its food 

 plant. As it is, a two days quest in the vicinity of Orono early 

 m September 1913 failed to locate a single colony which was not 

 well nigh demolished by Chalcid parasites and the colonies of 



*We have an exact parallel in Pemphigus tesseUata or the woolly 

 aphid of the alder with a cycle including a spring migration from the 

 maple leaf to alder and a fall or return migration to the maple and also 

 a generation of hibernating nymphs remaining under leaves about the 

 base of the alder during the winter and ascending to the stem before 

 feeding in the spring. 



