40 BULLETIX 100, U. S. DEPARTMENT OF AGRICULTURE. 
while both the adults and larvae of ladybirds feed on plant lice. 
Mr. E. K. Carnes, 1 experimenting hi the State Inseetarr at Sacra- 
mento ; Cal., found that 20 adult beetles of Hippodamia convergens 
averaged 21.8 aphides per day and that the larvae of this species each 
consumed from 250 to 300 plant lice during their larval existence. 
He found that adult females would deposit eggs for from a month to 
six weeks, laying on the average 15 eggs per day and feeding on the 
plant lice all the time. Essig 2 states that in the walnut orchards of 
Ventura County, CaL, OTla ahdominalis, the ashy-gray ladybird, is by 
far the most beneficial insect in the natural control of the European 
walnut aphis (Cliromapliis juglandicola). 
ARTIFICIAL CONTROL OF WALNUT APHIDES. 
The 'writer has been unable, save in one instance, 3 to find any pub- 
lished account of artificial control tried or adopted for walnut plant- 
lice. Until the year 1910 no such work seems to have been performed 
along this line. 4 In August of that year Mr. P. R. Jones, late of the 
Bureau of Entomology, carried out a series of laboratory experiments 
with a view to determining the efficiency of various washes against 
these aphides. A small hand pump was fitted with an Eddy-chamber 
nozzle and the applications made at a medium high pressure. Care 
was taken that not enough pressure was exerted to kill any of the 
''lice" by the force of the spray alone. Examinations were made 10 
minutes after the applications. From these experiments the fol- 
lowing results were obtained: 
Commercial tobacco extract No. 2, containing 40 per cent nicotine, at strengths of 
1-1,040 to 1-2,048, effective; dilutions weaker than 1-2,048, not effective. 
Commercial tobacco extract No. 1 containing about 4 per cent of nicotine at strength 
of 1-60, effective; dilutions weaker than 1-60, not effective (1-80 partially effective). 
Commercial tobacco extract Xo. 1, at strengths varying from 1-60 to 1-200, com- 
bined with a 3 per cent distillate-oil emulsion, effective. 
Commercial tobacco extract Xo. 2 at strengths varying from 1-1,000 to 1-2,650 com- 
bined with a 3 per cent distillate-oil emulsion, effective. 
Commercial tobacco extract Xo. 1 at strengths varying from 1-60 to 1-200 combined 
with a 2 per cent distillate-oil emulsion, effective. 
Commercial tobacco extract Xo. 2 at strengths varying from 1-1,000 to 1-2,620 com- 
bined with a 2 per cent distillate-oil emulsion, effective. 
Distillate-oil emulsion at 2, 3, and 4 per cent strengths, effective. 
Commercial lime-sulphur, 1-50, combined with commercial tobacco extract Xo. 1, 
1-100, effective. 
1 Sept., 1912. Carnes, E. K. Insectary Division Reports for the months of June and July, 1912. Mo. 
Bui. Cal. State Hort. Com., v. 1, no. 10, p. 820-S2S-. 
Some experiments -with the common ladybird ( Hippodamia convergens), p. 821-826. 
2 Apr., 1912. Essig, E. O. The walnut plant louse ( Chromaphis juglandicola [Kalt] Walker). Mo. Bui. 
Cal. State Com. Hort., v. 1, no. 5, p. 190-194, figs. 72-73. 
Control, p. 192. 
s Cf. Biennial Crop Pest and Hort. Report 1911-1912, Oregon Agr. Coll. Exp. Sta. Jan. 10, 1913, p. 165. 
" Blackleaf 40" and kerosene emulsion 10 per cent recommended. 
4 Since going to press control experiments undertaken in the spring of 1913 in Southern California by 
the University of California have been published in Circular 107 of tne Agricultural Experiment Station 
of the University of California. 
