4 8 



used at the rate of two ounces in a gallon of water ; liable to injure 

 foliage slightly. 



Stott's Fir Tree Oil Soap. — Altogether too expensive for use 

 against the insect, even though it were effective. 



Kerosene Emulsion. — Cheap ; troublesome to prepare ; effec- 

 tive as an insecticide, but requires syringing the leaves afterward to 

 prevent injury, at least in greenhouses when used on tomato plants. 



Permol Kerosene Soap.- — Too expensive ; fairly effective when 

 used at the rate of two ounces in a gallon of water. 



Bowker's Tree Soap. — Cheap ; most effective of all contact in- 

 secticides used in these experiments ; has advantage over the others 

 in requiring but one ounce in a gallon of water, making it less liable 

 to interfere with the respiration of the plants by forming a film over 

 the surface. While the odor of the soap itself is unpleasant, it is not 

 very objectionable when used in such a weak solution. 



Good's Potash Whale Oil Soap. — Cheaper by weight than Bow- 

 ker's Tree Soap, but when an amount is used which equals the latter 

 as an insecticide, the cost is about the same for the two soaps. One 

 and one-third ounces per gallon of Good's Soap is nearly as efficient 

 for use on the insect as one ounce of Bowker's Soap. More efficient 

 than laundry soap or Permol Kerosene Soap. The same may be 

 said of the odor as of Bowker's Tree Soap. 



Fumigants. The resistance of the greenhouse Aleyrodes to the 

 action of tobacco fumes is well known. The young, as might be ex- 

 pected from their mode of life, are entirely unaffected, while the adults 

 are only temporarily stupified by the same treatment with tobacco 

 that destroys most of the plant lice. The experiments with Nicoto- 

 cide and Thripscide show that these, also, are much more effective 

 on plant lice than on the adult Aleyrodes, while the experiments with 

 hydrocyanic acid gas show the remarkable susceptibility of adult 

 Aleyrodes to its action as compared with plant lice, the latter being 

 only stupified in the same atmosphere which was fatal to the former 

 Small amounts of the fumigants with a long exposure seem to be 

 more effective on the larva? and pupae than large amounts with short 

 exposures. 



Nicoticide. — The difference in the results of experiments i and 

 2 may be accounted for by the fact that in experiment i the tomato 



