Aug. 15. 1919 Derris as an Insecticide 199 



colored particles lay inside the integument; but most of them, if not all, 

 seemed to have been dragged there by the microtome knife, or washed there 

 by the staining liquid and xylol. However, a careful study of the par- 

 affin-ribbon sections, from the material dusted with the Derris powder 

 and carmine mixture, showed red powder only on the outside of the integu- 

 ment and none inside, except a small amount here and there in the 

 intestine. 



Mclndoo (6, p. 103) has shown tnat nicotme spray solutions not con- 

 taining soap do not pass into the tracheae of certain aphids and cater- 

 pillars, and the same is true for quassia-spray solutions not containing 

 soap. Quassia-spray solutions containing soap, however, pass freely into 

 the tracheae and finally reach the various tissues (7, p. 525). In view of 

 these results it was not considered necessary to trace Derris extracts con- 

 tained in water and in soap solution. 



The preceding histological study seems to show the followmg: Derris 

 powder dusted upon insects does not pass into the tracheae, but a limited 

 amount of it may lodge in the spiracles, though never sufficiently to inter- 

 fere with breathing. In order that the vapors and exhalation from a 

 . nicotine-spray solution be efifective, it is necessary for the insects sprayed 

 to carry some of this solution on their bodies; likewise it is necessary for 

 the insects dusted with Derris powder to carry some of this powder on 

 their bodies in order that its exhalation may pass into the spiracles in as 

 undiluted a condition as possible. After being dusted the insects seem 

 to swallow some of the powder, which later may act as a stomach poison. 

 Soap solutions containing Derris extracts pass freely into the spiracles 

 and finally reach the various tissues, but probably the extracts kill by 

 first affecting the ner\-e tissue. 



SUMMARY 



Derris, known widely as a pow^erful East Indies fish poison, was 

 found to fulfill several of the requirements of a general insecticide; it 

 acts both as a contact insecticide and as a stomach poison, but is of no 

 practical value as a fumigant. Six species of Derris were tested, but 

 only two of them {elliptica and uliginosa) were found to be satisfactory 

 for insecticidal purposes. 



According to the views of various authors, the toxic principle in Derris 

 is a resin, which affects the various classes of animals according to the 

 development of their nervous systems. It kills some insects easily and 

 others wath difficulty, but it usually acts slowly and seems to kill by 

 motor paralysis. 



Denatured alcohol was found to be a good economic solvent for ex- 

 tracting the toxic principle, which when applied in spray mixtures proved 

 to be efficient against certain aphids, potato-beetle larvae, and small 

 fall webworms. For proprietary insecticides it is possible to incorporate 

 the extracts from Derris into soft soaps which when greatly diluted 

 with water are readv for use. 



