THE PEA APHIS WITH EELATIOX TO FORAGE CROPS. 
5 
t3^pc specimens of trifolii arc 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 fflSTORY OF THE PEST AND ITS INJURIES. 
IN EUROPE. 
For at least a centur}^ the green dolphin," as tliis 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 m this instance was caused solely by the 
Aphis, and was universal throughout the kmgdom, so that a supply 
for the navy could not be obtained.'' 
In 1876 Buckton (7) whites 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 in 1885 
that country suffered from a great plague of pea '4ice," 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.^ 
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 wnrbellosen Thiere, die in Peutschland sowie in den ProAln- 
zen Preussen und Posen den Feld-, Wiesen- und M'eide-Cullurpflanzen sc hadlich werden. Bremen, 18C5. 
Also under title: Die der Landwirtlischaft Schudlichen Insecten und Wiirmer. 
