1 86 Journal of Agricultural Research voi. xvii. no. s 



been filtered and dried, a chocolate-brown powder resulted. This was 

 designated C. 



The chloroform extract from B was placed on a steam bath to remove 

 the chloroform. The residue resulting was a dark, sticky material which 

 became hard and brittle when cooled below room temperature. It was 

 ground while hard and was designated D. 



The three substances designated A, C, and D were tested in very dilute 

 form on small chinook salmon and were found to be exceedingly toxic. 

 The extract A appeared to be the most powerful, while the chloroform- 

 soluble resin D was much more toxic than was C. The effect of the 

 extract A on the fish might have been influenced to a considerable extent 

 by a trace of petroleum ether which seemed to remain in the extract and 

 imparted to it a distinct odor. 



The three substances called A , C, and D were tested also on small tent 

 caterpillars by being sprayed on foliage. Within eight days .4 had killed 

 70 per cent, C 92.3 per cent, and D 54.4 per cent of the caterpillars tested; 

 but only 22.1 per cent of the control lar\^ae had died. 



EXTRACTION OF DERRIS ELUPTICA AND TESTS OF EXTRACTS OBTAINED 



The roots of "tuba" or "toeba" were ground as fine as their fibrous 

 nature would permit, and 200 gm. of this powder were macerated for 

 two days with a quantity of cold water. After the mixture had been 

 filtered, the water extract measured 600 cc, each cc. representing K gm- oi 

 the roots. Half of this cold water extract was tested on small tent cater- 

 pillars ; within eight days only 30.9 per cent of them had died. The other 

 half of this extract was evaporated to one-half its volume on a steam bath 

 and then again made up to its original volume with water. This portion 

 of the extract was later tested on small tent caterpillars; within eight 

 days only 14.3 per cent of them had died. This does not mean that the 

 application of heat affected the toxicity of the extract, for 22.1 per cent 

 of the control larvae died. 



The marc from the preceding water extractions was dried by means of 

 a current of air and was macerated with several portions of cold petroleum 

 ether. The combined extracts were then divided into two equal portions. 

 While the petroleum ether evaporated spontaneously from one portion in 

 an open dish, it evaporated on a steam bath from the other portion. 

 The residue resulting was a waxy, yellow substance which represented 

 1.4 per cent of the original material. Spray solutions containing these 

 petroleum-ether extracts were tested on aphids ; there was practically no 

 difference in effectiveness between the extract obtained without the use 

 of heat and the one with it (see No. 288 and 289, Table IV). 



The powder left after the preceding extractions was spread out, and 

 the residual petroleum ether was allowed to evaporate. It was then 



