A-ug. IS. I9I9 Derris as an hisecticide i^'J 



divided into two equal parts; one part was macerated with successive 

 portions of cold 95 per cent alcohol until exhaustea, and the other part 

 was boiled on a steam bath with successive portions of 95 per cent alcohol 

 until exhausted. The combined extracts from the first part represented 

 4.17 per cent of the original powder and those from the second part 4.26 

 per cent. Spray solutions containing these alcoholic extracts were 

 tested on aphids, small fall webworms, and on large tussock-moth cater- 

 pillars. There was practically no difference in their effectiveness on these 

 insects (see No. 290 and 291, Table IV). 



EXTRACTION OF DERRIS ULIGINOSA AND TESTS OF EXTRACTS OBTAINED 



The stems were reduced to a coarse powder, and 100 gm. of this material 

 were repeatedly extracted on a steam bath with petroleum ether until 

 exhausted. Upon evaporation of the petroleum ether, there remained a 

 yellow, shiny, somewhat brittle substance which represented 1.02 per cent 

 of the original stems. 



The marc from the above extraction was dried thoroughly and then 

 exhausted with 95 per cent alcohol on a steam bath. The residue left 

 upon the evaporation ot the alcohol represented 7.82 per cent of the 

 stems. The above petroleum-ether and alcoholic extracts were found 

 very effective against aphids (see No. 293 and 294, Table IV). 



EXTRACTION OF VARIOUS SPECIES OF DERRIS WITH DENATURED ALCOHOL 

 AND TESTS OF EXTRACTS OBTAINED 



Since the preceding results have shown that alcohol is the most suit- 

 able solvent for the toxic resins, the use of denatured alcohol as the 

 best economic solvent was at once suggested. By the use of suitable 

 apparatus this solvent can be recovered with very little loss and con- 

 sequently can be used repeatedly. 



For the tests described below, 50 gm. of powdered material in each 

 instance were extracted with denatured alcohol on a steam bath, and the 

 extract was concentrated to 25 cc. so that i cc. was equivalent to 2 gm. 

 of material. 



In the tests performed in the laboratory, the general plan for each 

 test was to spray or dust about 500 aphids or 100 caterpillers on foliage, 

 and then to place this foliage in a bottle of water inside a battery jar 

 which was covered with cheesecloth. A record of the dead insects was 

 taken at regular periods. The tests with aphids usually covered a 

 period of 24 hours, and those with caterpillars and potato beetles 

 {Leptinotarsa decemlineata Say) 10 or 12 days. The results of most of 

 these tests are given in Tables IV and V. Table V gives chiefly the 

 results obtained by using denatured alcoholic extracts and the powders 

 of various species of Derris, applied as dust. Attention is called to the 



