510 



after about two weeks and feed extensively on the tissue, stems 

 and midribs of the leaves. They are most abundant during August 

 and early September and probably hibernate amongst fallen leaves 

 and rubbish. 



Grasshoppers in Okanogan County. — Washington State Dept. Agric. 

 Mthly. News Letter, Olympia, i, no. i, July 1919, p. 1. [Received 

 20th October 1919.] 



An account is given of a campaign for poisoning grasshoppers in 

 Okanogan County, Washington, carried out under the direction of 

 Mr. A. C. Burrell, upon whose research w^ork the campaign was based. 

 It was estimated that seven biUion eggs were laid in 1918. During 

 May and June, 1919, some three biUion of these have hatched over 

 an area of about 400 acres stretching into British Columbia, the 

 species concerned being Camnula pellucida. The breeding-places 

 were covered with numbers of small black hoppers, wliich were treated 

 with coal-oil, as many as 200 being frequently killed per square foot. 

 Those that survived marched in hordes into the winter and spring 

 wheat and were treated with the Government poison-bait of Paris 

 green in a salty mixture of mill feed and sugar-beet molasses flavoured 

 with imitation lemon extract. As many as four milhon hoppers per 

 acre were killed by this means, about ten pounds (5 lb. dry) of the bait 

 being used to the acre. Up to the time of WTiting, about £160 has 

 been expended on the campaign, practically the whole of the three 

 billion hoppers having been destroyed. The rapid action of the bait 

 enabled the wheat to spring up again and renew its growth, so that 

 the loss amounted to practically nothing, except in a few cases owing 

 to farmers' carelessness. The loss from grasshoppers in the same 

 district the previous year was computed at about £16,000 ; it is 

 impossible to forecast the damage that might have occurred in 1918, 

 if prompt action had not been taken at the time of hatching. 



Ball (E. D.). The Potato Leafhopper and the Hopperburn that it 

 causes. — Bienn. Rept. Wisconsin Dept. Agric. 1917-1918, Madison, 

 Bull. 20, 31st December 1918, pp. 76-102, 5 plates, 2 figs. 

 [Received 15th September 1919.] 



The bulk of the information here given on Empoasca mali has 

 previously been noticed [see this Review, Ser. A, vii, p. 278]. 



The remedial measures advocated are the use of a spray of Black- 

 leaf 40 at the rate of 1 part to 800 of water and 5 parts of soap. 

 Poisons may be added so as also to kill the potato beetle [Leptinotarsa 

 decemlineata] or the mixture without the soap may be added to Bor- 

 deaux mixture. Kerosene emulsion should be used as strong as 

 possible, so long as it does not cause scorching of the fohage ; 7-8 

 per cent, of kerosene or 1 part of stock emulsion to 8 parts of water 

 was found satisfactory. It is imperative that the under-sides of the 

 leaves should be reached with the spray. 



In Wisconsin about 5 to 10 per cent, of the eggs were found parasitised, 

 probably by a Dryinid, as yet unidentified. The only other natural 

 enemy is the fungus, Entomophthora sphaerosperma, which however does 

 not materially reduce the numbers of this pest. 



