38 FIRST ANNUAL REPORT OF THE STATE ENTOMOLOGIST. 



2. Application in fumes. — The powder burng freely, giving off considerable 

 smoke and an odor which is not unpleasant. It will burn more slowly when made 

 into cones by wetting and moulding. In a closed room the fumes from a small 

 quantity will soon kill or render inactive ordinary flies and mosquitoes, and will 

 be found a most convenient protection against these last where no bars are avail- 

 able. Insects of soft and delicate structure are affected most quickly. This 

 method will be found very effective against' insects infesting furs, feathers, her- 

 baria, books, etc. Such can easily be killed by inclosing the infested objects in a 

 tight box or case and then fumigating them. The method will also prove useful 

 in green-houses. 



3. Alcoholic extract. — The extract is easily obtained by taking a flask fitted 

 with a cork and a long and vertical glass tube. Into this flask the alcohol and 

 Pyrethrum is introduced and heated over a steam tank or other moderate heat. 

 The distillate, condensing in the vertical tube, runs back, and at the end of an 

 hour or two the alcohol may be drained off and the extract is ready for use. An- 

 other method of obtaining the extract, and a less expensive one, is by re-percola- 

 tion after the manner presented in the American Pharmacopoeia. The former 

 method seems to more thoroughly extract the oil. In either case, the extract is 

 more expensive than the other preparations, though convenient for preserving and 

 handling. 



The extract may be greatly diluted with water and then applied with any atom- 

 izer. Diluted with fifteen parts of water, it killed all the cotton worms in a few 

 minutes upon which it was sprayed. When mixed in the proportion of one to 

 forty of water, it killed two-thirds of the worms in twenty minutes and disabled 

 the remainder. A dilution of one to fifty still killed some of the worms and dis- 

 abled others.* 



4. Water solution. — This method of application is believed to be the simplest 

 most economical, and most efficient. The bulk of the powder is most easily dis- 

 solved in water, to which it at once imparts the insecticide principle. No constant 

 stirring is necessary, and the liquid is to be applied in the same manner as the 

 diluted extract. The finer the spray in which it is applied the more economical 

 is its use and the greater the chance of reaching every insect on the plant. Ex- 

 periments have shown that 200 grains of the powder (about one-half an ounce), 

 stirred in two gallons of water, was sufficient to kill all but the most hardy full 

 grown cotton-worms; but was not strong enough to kill some other larvas, es- 

 pecially such as are protected by dense long hairs. A solution of one-half of the 

 above strength would destroy young cotton-worms. The solution is most efficient 

 when first made, and gradually loses its power. On the third day it develops a 

 fungoid growth and its efficacy is then much impaired. 



5. The tea or decoction.— Proi. E. W. Hilgard, of California, who has experi- 

 mented with the Pyrethrum in this form, thinks that the tea simply prepared 

 from the unground flowers is the mostconvenient and efficacious method in which 

 it can be used. AVhen sprayed from a fine rose, he found it to be efficient even 

 against the armored scale-bug of the orange and the lemon, which fell off in two 

 or three days after the application, while the young brood are almost instantly 

 killed. Tea made from the leaves and stems has similar although considerably 

 weaker effects. The plants might be grown by the farmer and fruit-grower, 

 when, by simply curing the upper stems, leaves and blossomsall together, the tea 



*For a statement of the mode of preparation of the extract and experiments with it upon 

 the boll-worm {Heliothis armigera) and the cotton- worm, see the American Entomologist, 

 iii, 1880, pp. 252-3. 



