Entomological Xotes. 283 



was not effective. There were no insects that it did not destroy. 

 Spiders were quickly killed. House flies dusted with it, by a 

 little insufflator discharging the powder in the air, would soon fall , 

 dead from the ceiling, or while on the wing. It may be applied 

 in the powder state, mixed with flour or other light substance, or 

 with water, and sprinkled over the plants in the form of a spray, 

 or may be made into a tea or infusion, and be applied the same 

 way. The two last methods are the most convenient, the cheap- 

 est and most effectual, especially on trees and out-door plants, 

 but should be applied at a time when the evaporation would not 

 be rapid. In making the infusion, the leaves and stalks as well 

 as the flowers can be used, but the mixture will not have the 

 strength as when made from flowers alone. In making, the water 

 must not boil, as the volatile elements will thus be driven off. 

 Briskly boiling water should be used, then cover lightly and 

 steep slowly. From some experiments reported, there is reason 

 to believe that where the plant is raised among other plants, it acts 

 as a shield to them from the attacks of insect enemies. All 

 insects avoid the plant itself. 



Experiments with Pyrethrum. — The following are the ex- 

 periments alluded to by Prof. Henry as performed with this pow- 

 der by Prof. A. J. Cook of Michigan Agricultural College, taken 

 from the American Naturalist. 



September 27, 1880. 



I placed ten cabbage caterpillars {Pieris rapce, Schrank) in each 

 of two small wooden boxes which were'covered with wire gauze. 

 In one box I dusted the least possible amount of Pyrethrum 

 mixed with flour in the proportion of one part of the Pyrethrum 

 to twenty parts of the flour. I sprayed those in the other box 

 with a liquid mixture, using one tablespoonful of Pyrethrum 

 (seven grammes, one-fiftieth pound) to two gallons of water. In 

 five minutes all the larvie were on their backs ; nor did any of 

 them recover. A large number of the caterpillars on the cabbage 

 plants were sprinkled or dusted with theHPyrethrum, the propor- 

 tion the same as given above. In one hour the plants were ex- 

 amined, and in every case the caterpillars were found dead. 



