MAINE AGKICULTURAL EXPERIMENT STATION. 2qi 



summer, where it establishes a series of summer generations 

 and by fall produces a second migrant generation that flies back 

 to the original food plant. It is here the true sexes occur and 

 that the winter egg is deposited. — stages absolutely essential to 

 the continuation of the species. 



Such a dual personality of certain aphid species is a condition 

 which, before it is detected, betrays the economic entomologist 

 into many futile combative attempts ; but on the other hand the 

 same duality may reveal, when once discovered, the most vul- 

 nerable point of attack. It is not necessary to go out of our 

 own State for illustrations. The discovery that Chermes abieti- 

 colens, Thomas 1879, which makes cone-like gall? on black and 

 red spruce is the same species as Chcrmcs pinifoliae Fitch 

 1858,* which lays eggs on new growth white pine for progeny 

 that render the pine shoots weakened and unthrifty, gives the 

 landscape gardener his clue. If he treasures the beauty of a 

 group of white pines he would do well to exclude red and black 

 spruces from the vicinity, or conversely if he wishes to grow 

 black spruces with normal branches it is an indiscretion to place 

 them near wdiite pines. Again, when once it was ascertained 

 that the common Alder Blight, Pemphigus tesscUatus Fitch 185 1, 

 was masquerading on the maple (Acer sacchariiim L. — dasycar- 

 pimi Ehrh. and cultivated varieties) as Pemphigus acerifolii 

 Riley i879t the owner of ornamental cut leaved maples had a 

 theretofore unsuspected means of protecting their foliage by 

 the control of the pest on its alternate food plant, the alder, 

 which in many circumstances is an easy point of control. 



It is with no slight interest that we have ascertained that the 

 woolly aphid of the apple is such a migratory species with two 

 distinct types of food plants ; — the elm, or "original food 

 plant," on which the true sexes occur in the fall and deposit 

 the over-wintering egg, and on which it lives in the curled leaves 

 in the spring; and the apple to which it migrates from the elm- 

 leaf-curl and where it establishes itself as a bark feeder during 

 the summer. This species, in addition, produces in the fall a 

 generation that passes the winter at the roots of the apple, a 



* Bulletin 173 Maine Agricultural Experiment Station. 



t Entomological News, 1908, p. 484; Journal of Economic Entomol- 

 ogy 1909, Vol. II, p. 35; Bulletin No. 195 Me. Agr. Exp. Sta.. Feb. 13. 

 1912. 



