[22] REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



ricd into the chamber by rapid diffusion, and, affecting the worm, causes it to come 

 forth from its coucealmeut upon the moistened parts of the plant, where, by the con- 

 tact of the liquid, it is poisoned to death. The extract made with ethyl alcohol is 

 also volatile and produces this same effect, though in a less degree to the extent that 

 its -^^olatility is less than that of methyl alcohol. 



The extractive power of methyl alcohol on pyrethrum is so great that it is hardly 

 necessary to apply any heat ; the alcohol may be allowed to stand twenty-four hours 

 on the powder, being shaken up a few times and then the whole, i. e., both the ex- 

 tract and the solid residue, may be mixed with water, so as to give 100 gallons to the 

 pound of pyrethrum. 



I found that the use of the liquid is much to be preferred to the powder. It reaches 

 all parts of the plant better ; it is more easily handled and it kills quicker. 



EXPERIMENTS. 



1. Sprinkled powder on half dozen Heliothis in cotton blooms in the field. 



In a few minutes they left the blooms, crawled upon the leaves, fell to the ground 

 and attempted to crawl off; before going far they stopped and rolled over, as if in 

 pain, then crawled a little farther with further rolling and twisting. Aftei; some hours, 

 they were considerably shrunken, and became of a light yellow color instead of green. 

 I observed these until night ; when I left none were dead ; next morning, none of them 

 could be found. From this single exx)eriment, I would not have known whether the 

 worms died and were devoured by other insects during the night, or whether they re- 

 covered and made their escape ; but subsequent experiments satisfied me they must 

 have died. 



2. I tried a similar experiment on Heliothis, which I brought into the laboratory, 

 jjuttiug them in blooms and on leaves in such manner as to supply the natural condi- 

 tions. I applied the powder as above at 11 o'clock a. m. They were affected as those 

 in experiment (1,) except that they seemed to be more violently attacked. They 

 were not dead late in the afternoon; they were all dead next morning, the size of 

 the worms when dead being less than half their size before the application of pyreth- 

 rum. 



In these experiments, I was careful that some of tiie powder fell on each worm. Of 

 course, this would not be the case in ordinary field-work. My object was to see if, 

 when fairly applied, powder of this strength would kill insects. 



I found that insects with a thick chitinous covering frequently fl.ew away, not 

 seeming to be seriously affected. 



I tried this powder on Cabbage Worms ; it kills them when it touches them ; but 

 on cabbages the worms are so well protected by the width and arrangement of the 

 leaves that many escaped. 



It did not protect the cabbage plants, except for a short time, from the ilea beetle. 



3. August 27 I sprinkled extract pyrethrum, 1 part alcoholic (ethyl) extract to 20 ^ 

 parts of water, on a cotton plant where there Avere three Boll Worms. One of these 

 had penetrated a boll so far that only a small part was extended outside the boll ; 

 other two were on the flowers. In five minutes the worms were rolling and twisting, 

 falling to the ground ; died in a few honrs. 



August 30. Used same extract as above on three Boll Worms. Result substantially 

 same so far as Heliothis was concerned. Two young grasshoppers were quickly killed, 

 and a lady bird fell to the ground. It was -not dead, but struggling, as if in pain, 

 when night came on ; had disappeared next morning. 



4. September 17 : In the following experiment I used some of the same extract 

 spoken of in preceding exx)eriment. The quantity this time was half pint extract to 

 five pints water. I selected a spot in the cotton-field where Alctise were tolerably 

 numerous. There were three stalks of cotton growing close together, and the vines 

 of morning glory had densely intertwined themselves with these three plants, making 

 the foliage very thick and hard to penetrate. I caught a number of Aletise from other 

 stalks of cotton and put them on these until I could count 120. In all this time 

 neither I nor either of the gentlemen present to witness the experiment noticed a boll 

 worm (Heliothis). I used a small fountain pump made by Rumsey & Co., Seneca 

 Falls, N. Y. We sprayed the diluted extract over three rows for about 20 feet, throw- 

 ing more upon the three jjlants mentioned than elsewhere. Whilst the spray was fall- 

 ing upon this thick foliage I closely watched its effect ; to my surprise a large Helio- 

 this appeared on a leaf, seeming to be bewildered and making rapid exertions to get 

 off. On examination I found it had come from the interior of a full-grown boll on 

 which it was feeding ; the orifice it had cut was on the upper side, and I suppose some 

 of the fine spray passed through the orifice, and disturbing it in its excavations, caused 

 it to come forth. Soon after it appeared it crawled on a leaf which had been slightly 

 wetted with the extract, and in two minutes from the time the extract was thrown 

 on the plants this Heliothis fell to the ground, and after convulsions, rolling, crawl- 

 ing, twisting, which lasted an hour and a quarter, it died. In four minutes about 



