44 



THE AMERICAN ENTOMOLOGIST. 



the substance should be fresh, or should have 

 been kept lightly packed, for the same reason 

 that hops must be similarly treated. 



Hence I find that Milco's fresh powder is of 

 greater efficacy than the best imported, although 

 some of the latter contains twice as much matter 

 soluble in ether ; but the extract from the " bu- 

 hach" is a clear greenish oil, while that from im- 

 ported powder, and especially that from "Lyon's 

 magnetic" — ground-up refuse, stems, etc., as I 

 take it — is dark and thickish, or almost dry and 

 crumbl)'. 



Like all volatile oils, the essence of pyrethrum 

 is soluble in water to some extent, and the tea 

 froiTi the flowers, and to a less extent that from 

 the flower-stems and leaves, is a valuable and 

 convenient insecticide for use in the open air, 

 provided that it is used at times when it will not 

 evaporate too rapidly, and that it is applied in 

 the shape of spray, whose globules will reach the 

 insect despite of its water-shedding surfaces, hairs, 

 etc. Thus applied, I find that it will even pene- 

 trate the armor of the red scale bug — or rather, 

 perhaps, get under it — so that the bug falls ofl' 

 dead, in a day or two. The hairy aphides are 

 the most troublesome, and require a strong tea 

 of the flowers, atomized. The diluted alcoholic 

 solution can, of course, be made as strong as 

 you please, and will kill anything entomological. 



Some persons have tried the decoction, and 

 have of course failed, as the oil is dissipated by 

 boiling. 



My own experiments and those of Pro- 

 fessor Hilgard were made with the powder 

 from plants grown in California by Mr. 

 G. N. Milco, of Stockton, and this powder, 

 when used fresh, I have found to be more 

 powerful than the imported kinds. Mr. 

 Milco, a native of Dalmatia, has been cul- 

 tivating the P. cinerarictfoHum in Cali- 

 fornia in constantly increasing area for the 

 past three years, and deserves great credit 

 for his efforts in introducing it. The 

 California product is put upon the market 

 in neat bottles and packages under the 

 name of " Buhach," and I am under obli- 

 gations to Mr. Milco for the liberal supply 

 which he has placed at my disposal free of 

 cost, wherewith to carry on my experi- 

 ments. Before considering the cost of 

 using this insecticide in the cotton-field it 

 will be well to summarize the results of 

 these experiments. 



Pure Pyrethrum powder, mixed with a 

 small quantity of finely-powdered rosin, 

 was applied to the under-side of the leaves 

 by means of a small pair of bellows. Tak- 

 ing advantage of the direction of the wind, 

 and using the bellows freely, all the upper 

 leaves of the plants were found to be well 

 powdered, and consequently almost all the 



worms upon these leaves received at least 

 some particles. The smaller worms died 

 in convulsions in from lo to 20 minutes, 

 according to their size, and to the quantity 

 of powder they had received. Larger 

 worms soon became uneasy, and finally 

 felj to the ground, where they invariably 

 died in from 5 to 24 hours. 



Every attempt to restock with worms a 

 freshly-powdered plant failed. They evi- 

 dently do not like the smell of the powder, 

 and throw themselves from the leaves until 

 they either fall to the ground or reach a 

 leaf which has not been powdered. ■ 



Diluted with flour in varying proportions 

 from one part of each up to one part of 

 Pyrethrum and ten of flour, it produced 

 equally good results as when pure. Mixed 

 with 16 parts of flour, it proved at first in- 

 sufficient, but upon being kept in a tight 

 glass jar for two weeks, it evidently gained 

 in power, for it then proved almost as 

 effectual as the stronger mixtures. The 

 powder can be successfully sifted on the 

 plants during cloudy days or during the 

 evening when the worins are on the upper 

 side of the leaves. On sunny days, or 

 when the worms are just hatched, it is 

 more necessary to apply it to the under 

 side of the leaves, as it acts only when 

 coming in actual contact with the worms. 



A strong decoction of the powder applied 

 to the leaves produced no effect ; nor did 

 the worms appear to suffer from eating 

 leaves thoroughly soaked with this decoc- 

 tion. 



An alcoholic extract of the powder, 

 diluted with water at the rate of one part 

 of the extract to 15 of water, and sprayed 

 on the leaves, kills the worms that have 

 come in contact with the solution in a few 

 minutes. The mixture in the proportion 

 of one part of the extract to 20 parts of 

 water was equally efiicacious, and even at 

 the rate of i to 40 it killed two-thirds of 

 the worms upon which it was sprayed in 

 15 or 20 minutes, and the remainder were 

 subsequently disabled. In still weaker 

 solution or at the rate of i to 50 it loses in 

 efficacy, but still kills some of the worms 

 and disables others. I confidently recom- 



