16 BULLETIN NO. 3, DIVISION OF ENTOMOLOGY. 



EXPERIMENTS WITH PYRETHRUM. 



We treated so fully of this insecticide in our annual report for 1881-2 

 that the value of the powder and the modes of using it are now pretty 

 well understood. The following account of experiments made by Mr. 

 Howard will, however, prove interesting, as we had them instituted in 

 order to show how the different larvre experimented with were severally 

 affected by it. 



1. SPECIAL EXPERIMENT WITH CUTLERS' POWDER NO. 1. 



September 20, 11.45 a. m. — Three healthy, half-grown larva? of the 

 Fall Web-worm (Hyphantria textor) placed in small glass tumbler, and 

 a very small quantity of Cutlers' No. 1 puffed on the anterior abdomi- 

 nal segments of each ; tumbler covered with glass slip. 



In four minutes one seemed affected ; moved the head quickly from 

 one side to the other, arched the back, and made rapid jumping move- 

 ments as if trying to get rid of the powder. In b' minutes all were sim- 

 ilarly affected. At 7 minutes the one first mentioned was struggling 

 violently and incessantly, jumping and writhing the whole body, now on 

 its back and again on its side ; no intervals of rest except momentary 

 in this extremely rapid motion. 



In. ten minutes became quieter, but was still bending the body in all 

 directions ; incessantly writhing like a mammal poisoned with strych- 

 nine. 



12.2. — Motions have become more spasmodic and jerky, and have lost 

 to certain degree the smoothly writhing character. 



12.10. — Motions much slower and consist of a slow writhing of the 

 whole body. 



12.18. — Motion still slower ; the true legs trembling violently at in- 

 tervals. 



12.28. — The motion of the body has become very slow, but the legs 

 are constantly twitching. The rectum is somewhat everted and the ab- 

 dominal segments have become somewhat contracted. 



12.50. — The body is still more contracted, though still moving slightly,, 

 the legs still trembling somewhat. 



1.40. — The abdomen is still more contracted, but a slight motion is 

 left, which shows that the final paralysis is that of exhaustion rather 

 than of tetanus. 



2.00. — Apparently almost dead ; only a slight occasional motion of 

 prolegs and mouth parts, with an occasional twitch of one of the true 

 legs. 



3.20. — A very slight motion still perceptible ; the bodies have 

 shrunken to very small proportions. 



September 21, 9 a. m. — Still a slight motion of legs and mouth parts,, 

 and one moves also one of its prolegs. 



1.15 p. m. — No change. 



