404 



such comparatively low temperatures, the appHcation of heat in com- 

 bination with sifting and blowing may prove of some value. In experi- 

 ments on the effect of cold, a mite-infested sack of chaff was placed in 

 a chamber at 27° F. at noon ; 24 hours later, the temperature at the 

 centre of the sack had been lowered to 40° F., the mites being miaffected. 

 The sack was then taken into a chamber at zero and in 20 hours the 

 mites were all dead, the temperature in the centre of the sack being 

 17° F. Mites exposed to the rays of a 250 candle-power arc lamp died 

 within two hours. Only negative results were obtained in experiments 

 with pressure, in which half a dozen sacks of chaff were subjected to 

 pressure rising gradually to 35 tons. Hydrocyanic acid gas proved 

 unsatisfactory as regards penetrative power, mites being found ahve 

 in three sacks of chaff fumigated with the heavy dose of 6 oz. cyanide 

 of potassium in 100 cubic feet of space. The same three sacks were 

 subsequently exposed to the fumes of two sulphur candles for twelve 

 hours in the same airtight chamber. The mites were still living at the 

 end of this time and this result was also due to lack of penetrative power, 

 as death ensued when the mites were exposed directly to these fumes 

 for one hour. Laboratory experiments showed that carbon dioxide 

 was also effective when apphed directly to the mites. Carbon bisulphide 

 was found to have better penetrative power ; three sacks in which 

 6 oz., 12 oz., and 18 oz. respectively, were placed, were sewn up and 

 wrapped in a tarpauhn. After twenty-four hours, some of the liquid 

 was still unvolatilised and many living mites were found in each sack. 

 Seventeen hours later all the liquid had volatihsed, and tests made at 

 various parts of each sack yielded only a few living mites. It was 

 noted that the mites were often particularly abundant in the material 

 of the sacks, and this probably accounts for the fact that an improve- 

 ment in the condition of infested chaff may be seen when it has been 

 transferred from one place to another, the mites being shaken off the 

 outside of the sacks. Trials with hand sieves showed that the mites, 

 as well as any dust present, separated readily. No mites were found 

 in infested chaff after it had been well shaken in a sieve with 

 round holes of 1 mm. in diameter ; 227 grammes of infested chaff 

 yielded 1*52 grammes of dust and mites. 



The comparatively satisfactory results yielded by carbon bisulphide 

 caused this method to be employed on about 16,000 sacks. Bran was 

 satisfactorily treated in the same way. 



LouNSBURY (C. P.). Plant-killing Insects : The Indian Cochineal. — 

 Reprint from Agric. Jl. S. Africa, Pretoria, June 1915, 7 pp. 

 [Received 19th July 1916.] 

 This paper describes the use of the cochineal insect [Dadylopius 



cocciis] in controlling Ojmntia monocantha (prickly pear) in South 



Africa [see this Revieiv, Ser. A, ii, p. 440]. 



Caesar (L.). Insects attacking grapes. — Ontario Dept. Agric, Toronto, 

 Fruit Branch Bull. no. 237 (The Grape in Ontario), March 1916, 

 pp. 39-44, 4 figs. [Received 19th July 1916.] 



The chief grape pests in Ontario are Typihlocyha comes (grape leaf- 

 hopper), Haltica chalybea (grape-vine flea-beetle), and Macrodactylus 

 subsjoinosus (rose-chafer). Minor pests are Polychrosis viteana (grape- 

 berry moth), Fidia viticida (grape root-worm) and Oxyptilus perisceli- 



