66 
Pea-louse, or Clover-louse 
Macrosiphum pisi Kalt. 
(Nectarophora destructor) 
This is a big, green, long-legged plant-louse that has ruined mil- 
lions of dollars' worth of field peas and a great deal of red clover. It 
is the dominant species of its 
kind on these plants (Fig. 5) 
and can scarcely be confused 
with any other aphid. 
Distribution. — This pest 
was, in all probability, intro- 
duced with clover and peas 
from Europe, where it is 
widely distributed and com- 
mon, tho it is reported mostly 
from England, Germany, 
France, and Italy. In the 
United States it has been in- 
jurious in Maine, New Hamp- 
shire, Vermont, Massachu- 
setts, Connecticut, New York, 
New Jersey, Pennsylvania, 
Delaware, A'laryland, the Dis- 
trict of Columbia, Virginia, 
North Carolina, Ohio, Illinois, 
Michigan, Wisconsin, Minne- 
sota, Nebraska, Iowa, Ken- 
tucky, and Texas. It is wide- 
spread in Canada also, occur- 
ring in Nova Scotia and New 
Brunswick and westward thru Ontario. 
Not until 1899 did the louse attract the attention of American 
entomologists ; in that year an outbreak in Maryland was reported 
upon by W. G. Johnson. He and E. D. Sanderson have written most 
of the literature on the species. 
Our personal observations of several years, made as independ- 
ently as possible, have yielded many facts that were already known 
and many that are new. The present account refers especially to the 
insect as it occurs in Illinois. In the eastern states the insect is chiefly 
a pest on peas. Here, where peas are not grown extensively, it is 
a pest on red clover. 
Food Plants and Injury. — Under the name of "green dolphin" 
this aphid has long been known in Europe for its injuries to peas and 
vetches, and in minor measure to clovers and various weeds — some 
forty plants in all. 
In America the aphid has done immense damage to peas and 
clovers. It affects especially leguminous plants, but numbers also 
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Fig. 5. — Clover-louse, Macrosiphum pisi, on stems 
of red clover. Natural size. 
