30 PROTECTION OF PLANTS, 1915-16 



the first American account of its life economy. Since then several shorter 

 articles have appeared from time to time but generally these have been 

 only re-statements of the work of others. 



This species always passes the winter as tiny, black, oval eggs scattered 

 indiscriminately over the tender succulent twigs and branches, around 

 fruit spurs and leaf buds, rarely on the larger branches. The eggs hatch 

 in early spring just as the flower buds are showing green (that is about 

 April 21 at Ithaca, N.Y. in 1915). The eggs continued to hatch till May 

 2nd though the greater majority hatched during the first four or five days. 

 Of course, hundreds and thousands of the eggs fail to hatch owing to 

 various not well known causes. This is fortunate for should all the eggs 

 laid in any one fall hatch the following spring the infestation would be 

 almost beyond our conceiving. 



The stem mothers, as the young hatched from the eggs are called, 

 attack the opening leaves and soon conceal themselves in the hairs deep 

 down in the unfolding bud. They reach maturity in about fourteen to twen- 

 ty days, that is between May 11 and 14th (at Ithaca, N.Y.). At this time 

 the apple trees are just beginning to come into full bloom and give ideal con- 

 ditions for the young from the stem mothers to cluster on the opening flowers. 

 The stem mothers reproduce very actively, commencing within twenty- 

 four hours of their last molt, and continue to produce over a period of 30 

 days or more, that is till about the middle of June. Each stem mother gives 

 birth on an average to about 59 young. Many, however, produce more, 

 but in my experiments this was the average for five individuals under 

 fairly normal conditions. 



The second generation reaches maturity in 12 to 14 days, and the great- 

 er majority are winged viviparous females. These fly readily from tree to 

 tree and orchard to orchard and soon spread the species very rapidly. The 

 reproductive capacity of winged females is much lower than that of the 

 stem mothers and the period of reproduction is shorter. From now on 

 throughout the summer generation succeeds generation of winged or wing- 

 less females with great rapidity and if natural enemies are not abundant 

 and no artificial control measures have been used by the fruit growers 

 severe injury and loss of the crop is bound to follow. 



The habits of the species are in rather marked contrast to those of the 

 rosy aphis. They congregate most commonly on the tips of the tender shoots, 

 on the under surface of the leaves, and when abundant, like the rosy aphis, 

 they attack the developing fruit. Crowding on the rapidly growing shoots 



