April, '10] GILLETTE : INSECTICIDES FOR APHIDS 209 



Sulphate of Nicotine was used 54 times in strengths varying be- 

 tween 1 in 50 and 1 in 500 and in no instance did an egg hatch. The 

 species used were A. pomi, A. coniifolice, A. viburnicola, Ch. negiindi- 

 nis, Mel. smithice, and BIy. elceagni. The last named species was not 

 treated with dilutions below 1 to 150. Eight applications of 1 to 750 

 resulted in a few hatching in one instance only. In weaker dilutions 

 the number hatching gradually increased. 



Nico-Fume was used in 55 applications in which the dilutions 

 varied between 1 in 50 and 1 in 1,000 and in no case did a single Qg^ 

 hatch. In 1 to 1,200 some hatched; in 1 to 1,500 more hatched, and in 

 1 to 1,800 stiU more. 



I hardly dare give out these results with the tobacco preparations; 

 they are too good. I shall not fully believe them myself until I have 

 tested them out another year with similar results. 



All the applications that I am reporting were made in an insectary 

 and the eggs were treated by dipping the twigs bearing them 3 or 4 

 times in quick succession into the various insecticides and then setting 

 the twigs in moist earth in the insectary to be under observation until 

 the lice hatched or until all hope of hatching was past. 



Results With the Lice 



Time will not permit me to go into this part of the work except to 

 state that, in a general way, the results with the nicotine preparations 

 run parallel with those above given. Black Leaf killed most lice well, 

 down to a 1 per cent dilution and Sulphate of Nicotine and Nico- 

 Fume killed most lice, well down to 1 part in 1,000, Nico-Fume having 

 somewhat the advantage over the Sulphate in results. 



In closing I would like to call attention to the fact that there is a 

 great difference in different species of the Aphididas as to their power 

 to resist the action of contact insecticides. The eggs of Chaitophorus 

 negundinis were more easily killed than those of any other species 

 that I have worked with while the eggs of Myzus elceagni were the 

 most difficult to destroy. I have found a thorough application of either 

 Sulphate of Nicotine or Nico-Fume in the proportion of 1-1,000 to 

 either Aphis pomi or Schizoneiira lanigera will kill 100 per cent of 

 those actually treated, while a similar treatment of the black chrysan- 

 themum louse, Macrostphum sanborni, will not kill one. Even 1 

 part in 100 is hardly strong enough to kill the latter species well, and 

 1 part in 200 is very inefficient, if used in the usual manner. 



I find, however, by adding a small amount of soap, 1 pound to 50 

 gallons, the efficiency of these tobacco extracts is greatly increased. 



