16 



LIFE HISTORY OF THE ALDER BLIGHT APHIS. 



October 5, 1905. — Large numbers of return migrants were found on 

 the trunks of many of the maples near Rosslyn, Va., while on alders 

 near by some colonies of Pemphigus tessellata, composed of apterous 

 females, accompanied by numerous larvae of the hibernating series , 

 and numbers of return migrants, were observed. A comparison of 

 these mijrrants with those found at the same time on the trunks of 

 maples, or with those of the first series, termed Pemphigus acerifolii, 

 proved them to be absolutely alike. These return migrants to the 

 maples were scattered over the trunks of the trees from the bottom 



to at least- 50 feet above 

 the ground, or as far up as 

 the eye could reach, re- 

 sembling flakes of snow. 

 Frequently as many as 20 

 or more were counted in 

 some of these batches. 



With the migrants were 

 also numbers of the tnie 

 sexes, many of them 'in 

 copula. Some of these 

 females had crowded into 

 such small cracks that it 

 seemed almost impossible 

 for them to do so ; 34 speci- 

 mens of both sexes were 

 found between and under 

 some old spider webs, while 

 near them under a small 

 piece of loose bark were 

 110 of the sexual females, 

 closely packed. There 

 were also winter eggs in 

 groups of two or more, 

 slightly covered with or 

 embedded in a delicate 

 layer of white wool. The 

 empty females were colorless and generally died some distance from 

 their egg, though sometimes a dead female was found with the egg 

 still attached to it. 



July 19, 1906. — Near the Chain Bridge, District of Columbia. 

 Failed to find Pemphigus acerifolii on leaves of maple, nor were any 

 migrants observed on leaves of alders. I discovered, however, 3 

 colonies of the hibernating series, some of which w^ere already ma- 

 ture females, accompanied by hundreds of young larvae, distributed 

 in patches of 5 to 10 or more, all arranged in circles, with their 



Fig. 2. — Prociphilus tesselata: Return migrants 

 on trunk of maple. (Original.) 



