568 



abandoned and a fresh one chosen, to wndward of the previous patch, 

 if near at hand, as the crawhng stages are carried by wind. The 

 heads before planting should be dipped in lime-sulphur solution diluted 

 in the proportion of 1 gal. concentrate (32) to 10 gals, water, the 

 formula used being 4 lb. fresh stone lime, 8 lb. sulphur, 2 gals, 

 water. Kerosene emulsion diluted with 4 parts water to one part 

 emulsion might be substituted. Experiments are needed to determine 

 the exact strength of either lime-sulphur or kerosene emulsion necessary 

 to kill this scale on the growing vines without injury to the fohage. 

 Spraying should, however, be considered as merely supplementary 

 to careful treatment of the heads at the time of planting. 



Black Fly. — Jl. Jamaicct Agric. Soc, Kingston, xxi, no. 9, September 

 1917, p. 381. 



The black fly of citrus trees [Ahurocanlhus tvoglumi] causes much 

 damage in Jamaica, and spraying with petroleum emulsion is a tedious 

 and expensive ])rocess. It is considered probable that the ant recently 

 discovered as predaceous on the scale [see this Review, Ser. A, v, p. 238] 

 will prove to be the best control. 



SwAiNE (J. H.). Shade Trees and Forest Insects in Manitoba. — Agric. 

 Gaz. Canada, Ottawa, iv, no. 9, September 1917, pp. 755-763. 



This paper contains notes on the shade-tree pests of Manitoba, 

 many of which have been previously dealt with [see this Review, 

 Ser. A, iv, p. 249], and gives general directions for spraying, with 

 formulae for the sprays most usually employed. 



Destructive insects in the forest area include Lygaeonematus {Nema- 

 tus) erielisoni (larch sawfly), which, recently introduced from Ontario, 

 is now firmly established in Manitoba and has spread westward into 

 northern Saskatchewan. The larvae are sometimes so numerous as 

 to defoliate the trees. There are several native parasites, but they 

 are seldom able to check the pest before the trees have been seriously 

 injured. Parasites that are an effective check in England have been 

 distributed in Manitoba and it is hoped that they will prove an impor- 

 tant means of control. Cultivated larches should be sprayed ^vitli 

 lead arsenate or Paris green. 



DoANE (K. W.). Effect of Smelter Gases on Insects.- — Science, 

 Lancaster, Pa., xlvi, no. 1186, 21st September 1917, pp. 295-296. 



It has often been asserted that the waste gases, especially sulphur 

 dioxide, evolved during the smelting of copper, lead and other ores, 

 have such an injurious effect on insect life in the vicinity, that even 

 fruit crops have been affected owing to the lack of bees to insure 

 pollination. Experiments to test the truth of this have been con- 

 ducted during the past three years, and it has been proved conclusively 

 that sulphur dioxide, even at a concentration of 25 parts in a million 

 of air, which is a nmch higher percentage than. that of the gas from 

 the smelters, has no effect whatever on flies, mosquitos, leaf-hoppers, 

 grasshoppers or Coccinellid beetles. Though burning 2 lb. sulphur 

 for every 1,000 c. ft. of space results in a concentration of 24,000 

 ])arts of gas to a million of air, prolonged fumigation even at this 

 rate sometimes fails to kill all the insects concerned. 



