14 
BULLETIN 112, U. S. DEPARTMENT OF AGRICULTURE. 
o/cenxe at La Fayette. Ind., and "Washburn i says that this plant-lou^e 
is attacked by a "red mite." Of the ladybird beetles which attack 
this aphis. Fitch mentions Eippodamia parenthesis Say, Coccinella 
9-notata Herbst, and Coccinella o-notata Kirby. although it seems 
probable that Fitch was dealing with a different plant-louse, and he 
may not have observed them feeding on the oat aphis. At different 
times assistants of the Cereal and Forage-Crop Insect Investigations 
have observed the following ladybird beetles, or their larva?, feeding 
on the oat aphis in various parts of the United States: Cyeloneda 
munda Say. Coccinella 9-notata Herbst, Megilla macvdata DeG.. 
Scymnus sp., and Hippodamia convergens Guer. 
(fig. 9), the last species being by far the most 
abundant, and consequently the most useful of 
the coccinellids in the control of the aphis. 
In addition to the foregoing enemies, the 
larvae of several species of lace-wing flies 
(Chrysopidae) are known to feed upon -this 
aphis. 
Miss Margaret Morse, of "Worcester. Mass.. 
(in litt.) has found that quails eat these aphides 
in confinement, and while definite field observa- 
tions are lacking, it is quite probable that the 
quail, or bobwhite. as well as other birds fre- 
quenting grain fields, plays an important part 
in the control of this and other grain aphides. 
Among other natural agencies which assist in 
holding the aphis in check are fungous diseases. 
These, like most fungi-attacking insects, thrive 
best under moist conditions ; hence the diseases 
commonly attacking plant-lice are most preva- 
lent and useful in moist seasons. Rains likewise 
have a beneficial effect, particularly ;; driving " 
rains. 
Webster, 2 in his Ohio report. " suspects " two 
minute insects. Gonatocerus orunneus Ashm. [MS.] and Polynema 
longipes Ashm. (Cosmocena citripes Ashm.) as destroying eggs of 
avenm, but this observation has apparently never been authenticated. 
Fig. 7. — Dead aphides, 
showing holes from 
which the matured par- 
asites of Apliidius tes- 
taceipes emerge. The 
top figure shows the 
lid still attached, but 
pushed back ; the bot- 
tom figure shows the 
parasites emerging. 
Enlarged. (From Web- 
ster/) 
REMEDIAL AND PREVENTIVE MEASURES. 
As in the case of the well-known spring grain-aphis, or " green 
bug"' (Toxoptera gramium). it is practically impossible to control 
1 Twelfth Rpt. State Entomologist of Minn, for 1907 and 190S, Dec, 190S, p. 50. 
2 Op. cit., p. 117. 
