THE PEA APHIS WITH RELATION TO FORAGE CROPS. 
53 
lahns Muls., Adalla hi punctata L., aiul ChUocorus hivulnerus Mills. 
Both larva3 and adults feed on the plant lice. 
The larvtT? of the syrphid flies (Syrphidae), more generally known 
under the name of ''sweat bees," are important enemies of the pea 
Fio. ir>.—Allograpta o6'jgMa, a sjTphii fly -he larva of u Inch preys upon ^fncrosiphuJn pisi. (Oriirinol.) 
aphis. The larvae are sluglike and attack the aphis hy piercing it 
and sucking the body juices. Each larva is capable of devouring 
many aphides in rapid succession. Johnson reports (1899) that one 
grower in Maryland, when separating peas, sieved out 
about 25 bushels of syrphid larva^, mostly of the spe- 
cies AUograpta obliqua Say (figs. 15, 16), which is illus- 
trative of the abundance of these larvic at times. The 
adult flies are everywhere abmidant in summer, and 
especially in the neighborhood of heavy aphis infesta- 
tions. They hover in the air and at brief intervals fly 
rapicUy, but only for short distances. Folsom (1909) 
enumerates eight species as attacking MacrosipJium 
pnsi, namely, Ocyptamus {Bacclia) fuscipenms Say, 
PlatycJiirus quadratus Say, Syrp)hus amencanus Wied., 
S. rihesii L., AUograpta obliqua Say, Mesogramma mar- 
ginatum Say, M. politum Say, and Spliaeropliona cylin- 
drica Say. 
Three species of lace-wing fly larvi^ (ClirysopidaO, 
namely, Clirysopa oculata Say, C. rnijilahis Burm., and 
C. plorahunda Fitch, feed on this plant louse. They 
are predacious in the larval stage, as is the case witli 
the syrphids. The larvie are provided with a pair of 
hollow bow-shaped mandibles or jaws, with which they 
grasp the aphis and through which its juices are sucked. The 
adults are pale green insects with relatively large lacelike wuigs, and 
from this character the common name is derived. 
Fig. us.— AUo- 
grapta obliqua: 
I.arva. Much 
en 1 a r g d . 
(From Metcalf.) 
