ENTOMOLOGY. 773 



solution of cak'iuin sulphid were badly affected. Petroleum emulsion 

 was less injurious than any of the other insecticides. In cases where 

 the bushes were lifted and dipped in solutions of carbolic acid or 

 calcium sulphid of various strengths, the results were equally 

 unpromising-. 



Another series of experiments was carried on from December, 1898, 

 to October, 1899. Each experiment involved 60 currant bushes, half 

 of which were Baldwins and half Black Naples. The substances 

 employed in these experiments were undiluted methylated spirits, 

 naphtha and saturated solutions of naphthaline in naphtha, formalin 

 in 2, 0.6, and 0.1 per cent solutions, undiluted kerosene, and kerosene 

 emulsion in 2 strengths. In none of these experiments did the insecti- 

 cide treatment have any effect on the mites. No appreciable eff'ect on 

 the foliage was produced bv the methylated spirits, naphtha, naphtha- 

 line, or formalin. In the use of kerosene emulsion it was noted that 

 so long as weaker grades were used, the injury to the foliage was 

 greater as the strength of the solution increased. AVhen much greater 

 strengths were used, there was much less injury, and in the case of 

 pure petroleum there was no injury whatever to the foliage. The 

 authors explain this result by the insolubility of kerosene in ^v^ater, 

 the coating of moisture on the leaves preventing it from coming into 

 direct contact with the leaf tissue. An increase as well as a decrease 

 in the strength of the kerosene emulsion beyond a certain point ma}^ 

 render the emulsion less injurious to the foliage and also less destruc- 

 tive to insects. 



A series of experiments was conducted for the purpose of deter- 

 mining whether this species of mite may not find shelter in the ground 

 or about the roots of currant bushes as well as in the buds. The 

 experiment showed conclusively that the mite does not hibernate 

 anywhere except in the buds and that infestation maj^ often be 

 due to transportation of the mites by wind. The authors exper- 

 imented with hydrocyanic-acid gas during which 1 oz. of potas- 

 sium cyanid, 1 oz. of sulphuric acid, and 2 oz. of water were used 

 for every 150 cubic feet of space. In order to confine the gas the 

 plants were covered with a box which was inclosed with tarred felt. 

 After this treatment the mites were found to bo uninjured. Another 

 insecticide, consisting of a solution of nicotin and camphor in diluted 

 alcohol, was tried with negative results. Dipping currant bushes in 

 water at various temperatures was found to furnish a rather efficient 

 means for destroying the mites. A 5 minute immersion in water at 

 115^^ F. destroj'ed the adult mites but did not destroy the eggs. Higher 

 temperatures, such as l-tO or 160*^ F., were found to produce disastrous 

 effects upon the currant bushes. A general inspection of infested 

 bushes disclosed the fact that in any particular variety the infestation 

 by mites was most pronounced in the strongest and healthiest bushes. 



