14 



BULLETIN 112, U. S. DEPARTMENT OP AGRICULTURE. 



avence at La Fayette, Ind., and Washburn 1 says that this plant-louse 

 is attacked by a " red mite." Of the ladybird beetles which attack 

 this aphis, Fitch mentions Hippodamia parenthesis Say, Goccinella 

 9-notata Herbst, and Goccinella 5-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 larvae, feeding 

 on the oat aphis in various parts of the United States: Cycloneda 

 munda Say, Goccinella 9-notata Herbst, Megilla maculata DeG.. 

 Scymnus sp., and Hippodamia convergent Guer. 

 (fig. 9), the last species being by far the most 

 abundant, and consequently the most useful of 

 the coccinellicls in the control of the aphis. 



In addition to the foregoing enemies, the 

 larva? of several species of lace-wing flies 

 (Chrysopida?) 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. Eains likewise 

 have a beneficial effect, particularly " driving " 

 rains. 



Webster, 2 in his Ohio report, " suspects " two 

 minute insects, Gonatocerus brunneus Ashm. [MS.] and Polynema 

 longipes Ashm. (Gosmocena citripes Ashm.) as destroying eggs of 

 avena3, but this observation has apparently never been authenticated. 



Fig. 7. — Dead aphides, 

 showing holes from 

 which the matured par- 

 asites of Aphidius tes- 

 taceipes emerge. The 

 top figure shows the 

 lid still attached, but 

 pushed back ; the bot- 

 tom figure shows the 

 parasites emerging. 

 Enlarged. (Prom 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 1008, Dec, 1908, p. 50. 



2 Op. cit., p. 117. 



