THE PEA APHIS WITH RELATION TO FORAGE CROPS. 5 



type specimens of trifolii are given in the descriptive paragraphs. 

 Pergande listed a variety of hosts attacked by trifolii, and although 

 we have not seen specimens other than the types which were col- 

 lected on Trifolium pratense, we doubt the correctness of its occurring 

 on such plants as strawberry, dandelion, wheat, and oats, food plants 

 noted by Pergande. 



Through the kindness of Dr. Albert Tullgren, of Sweden, Drs. 

 Mordwilko and Cholodkovsky, of Russia, Prof. F. V. Theobald, of 

 England, and Dr. G. Del Guercio, of Italy, we have been able to 

 compare the American pisi with specimens from the foregoing 

 countries and find them to be identical. 



PAST HISTORY OF THE PEST AND ITS INJURIES. 



IN EUROPE. 



For at least a century the "green dolphin," as this insect is com- 

 monly known in England, has been a serious pest to peas, vetches, 

 and clover. One of the earliest records of injury is that given us in 

 1815 by Kirby and Spence (2), who reported that in 1810 "the 

 produce was not much more than the seed sown; and many farmers 

 turned their swine into their pea fields, not thinking them worth 

 harvesting. The damage in this instance was caused solely by the 

 Aphis, and was universal throughout the kingdom, so that a supply 

 for the navy could not be obtained." 



In 1876 Buckton (7) writes that this insect "in some years is very 

 destructive to the farm crops. It feeds on a large number of plants, 

 but chiefly it infests the field pea, on the young shoots and leaves of 

 which it clusters by thousands." Thus the pea aphis seems only to 

 have been occasionally and locally injurious in England; but hi 1885 

 that country suffered from a great plague of pea "lice," and this 

 unusual abundance has been correlated with the slight precipitation 

 during that year. In her report for 1885, Miss Ormerod (8) notes 

 that this plant louse particularly damaged peas and vetch. 



As has been stated by Mordwilko (10) : 



In North Europe the pea louse lets itself be heard from only occasionally. For 

 instance, Kaltenbach (1843-1872) and C. Koch (1857) mention nothing at all about 

 damage by the pea louse. Only E. Taschenberg notes briefly that the pea louse is 

 occasionally very injurious to peas on which it hinders the further growth of the tips 

 of young runners. 1 



Quoting further from Mordwilko (p. 36) : 



In Russia as in N. Europe field peas suffer only occasionally from pea lice, namely, 

 when the latter succeeds to increase greatly by the time or before peas come into 

 bloom * * *. 



1 Taschenberg, E. L. Naturgeschichte der wirbellosen Thiere, die in Deutschland sowie in den Provin- 

 zen Preussen und Posen den Feld-, Wiesen- und Weide-Culturpflanzen schadlich werden. Bremen, 1865. 

 Also under title: Die der Landwirthsehaft Schadliohen Insecten und Wiirmer. 



