1919] ECOFOMIO ZOOLOGY — ENTOMOLOGY. 663 



and others. Studies relating to the insect in its transmission of spinach blight 

 have been previously noted (E. S. R., 89, p. 550). 



The year 1917 is apparently the first time this species proved to be generally 

 injurious over a large territory. In the Virginia trucliing region injury to po- 

 tatoes was first noticed In 1914. Outbreaks were more or less local in 1915, 

 while the most severe outbrealis occurred during 1916, 1917, and 1918, varying 

 from 1 or 2 to 75 or 80 per cent. It has been the source of considerable injury 

 to young eggplant in cold frames and to the blossom and young fruit. Often 

 its injury to tomatoes may occur chiefly on the blossom chisters and terminal 

 shoots, the production of fruit being thus stopped ; otherwise it resembles that 

 to potatoes. During outbreaks of the green pea aphis (M. plsi) on peas in 1914 

 and 1915 the relative abundance of M. solanifolii varied from 13 to 42 per cent. 



Although spinach has been severely injured by the attack of aphids for the 

 past 12 or 15 years, the green peach aphis (Rhopalosiphum persiccc) has in tlie 

 past probably caused the greater direct loss. During the past 5 years, however, 

 the potato aphis has become numerous and in 1915, 1917, and 1918 serious out- 

 breaks occurred on spinach during the fall and winter months. In those cases, 

 while R. persicw was present, over 90 per cent of the aphids infesting the crop 

 were M. solanifolii. While it reduces both the yield and market value of 

 spinach the greatest loss Is caused through transmitting the spinach blight. 

 The loss occasioned by this disease, transmitted by both M. solanifolii and R. 

 persicw, has been estimated to exceed $200,000 annually, which is approximately 

 20 per cent of the value of the entire crop. 



In a study of its host plants it was found to feed and reproduce on 61 

 species representing 19 families. In the region of Norfolk it does not produce 

 true sexes, the species passing the entire year as viviparous females. On the 

 Eastern Shore peninsula the true sexes are produced occasionally, but are not 

 eommon, 



" Beginning about the first of March, there occurs a period lasting nearly six 

 weeks when the aphids leave their winter host plants and colonize on a large 

 variety of weeds, and also asparagus and potatoes. The aphids remain on as- 

 paragus only while the shoots are young and succulent. Potatoes are usually 

 infested first when they are from 1 to 3 in. tall. The date depends largely on 

 the prevailing climatic conditions. The general migration ceases about the first 

 of May, although siwradic flights occur later. During the excessively hot 

 weather, especially if it is dry, little movement takes place among the aphids. 



" M. solanifolii is relatively abundant on various weeds until about July 1 to 

 15. Increased numbers of their natural enemies decimate the species, and 

 during the late part of July and August they are exceedingly scarce and dif- 

 ficult to locate. Except when the aphids are sufficiently numerous to destroy 

 the vines, there has not been observed any general migration from the spring 

 crop of potatoes to other crops or weeds. It is believed that the offspring of 

 Individuals, which migrate to weeds early in the spring, are the ones which 

 survive the summer. 



" By the first of September the aphids are beginning to be more numerous 

 on weeds, and an intermittent period of migration occurs which lasts until the 

 weather becomes cold, usually about November 15. Young kale is occasionally 

 heavily infested for a short period, but most of the aphids eventually find their 

 way to spinach. Scattered individuals are to be found throughout the winter 

 on certain of the Cruciferse and Leguminosse. The fall potato crop rarely suf- 

 fers as severe injury as the spring crop. Outbreaks may occur on spinach at 

 any time during the winter when the weather couditiijns are favorable. Hard, 



