Aug. IS, 1919 Derris as an Insecticide 197 



PHARMACOLOGICAL EFFECTS OF TOXIC PRINCIPLE 



The preceding experiments show that the toxic principle contained in 

 Derris kills insects both as a contact insecticide and as a stomach poison. 

 It now remains to be shown how this poison kills insects. This phase of 

 the work involves a careful study of the physiological effects of the toxic 

 principle on insects and of how it reaches the internal tissues. 



PHYSIOLOGICAL LFFECTS 



In the foregoing experiments it was observed that the various spray 

 mixtures and powders were effective only when they came in actual 

 contact with the insects tested. The following experiments were per- 

 formed to determine whether they would kill insects without coming in 

 actual contact with them. In these experiments only the powder from 

 Derris sp. was used. 



Ten small fall webworms, confineo in an observation wire-screen case, 

 were placed }i inch above the surface of a strong mixture of Derris 

 powder and water so that the exhalation and vapors from the mixture 

 could pass freely through the wire screen. No effects on the insects were 

 observed which could be attributed to the presence of the insecticide. 



Fall webworms, ants {Monomorium pharaonis L.), various species of 

 aphids, roaches, and the larvae of Prodenia ornithogalli Guenee were con- 

 fined in large, air-tight glass tubes with Derris powder so that they could 

 not touch it. As a rule, the exhalation from the powder had little effect 

 upon the confined insects. None of the webworms or larvae of Prodenia 

 died, and only a small percentage of the ants and aphids and only the 

 recently hatched roaches succumbed. 



Most of the aphids dusted with Derris powder fell within a few hours 

 in a paralyzed condition from the plants bearing them, and then they lay 

 more or less helpless for a few hours before they died. Aphids sprayed 

 with Derris mixtures and extracts behaved almost normally and showed no 

 symptoms of paralysis; in short, they died very slowly and their behavior 

 was similar to that of those sprayed with quassia extracts, described by 

 Mclndoo and Sievers (7, p. 523). Honeybees fed extracts of Derris 

 seemed to die of motor paralysis; and their behavior was similar to that 

 of those fed nicotine, described by Mclndoo (<5, p. pj); but it was some- 

 what different from the behavior of those fed arsenic. 



HISTOLOGICAL METHODS OF TRACING DERRIS POWDER AND SPRAY MIX- 

 TURES IN INSECTS 



Small individuals of fall webworms, caterpillars of Datana, silkworms, 

 and cockroaches, confined in wire-screen observation cases, were dusted 

 with Derris powder (No. 200) . Three hours later all of them were " stupid," 

 and after being removed from the cases they were put in vials containing 

 thick celloidin. After remaining in the celloidin an hour they we're put in 

 other vials containing chloroform. Then an hour later they were cut into 



