~ 2 - 
1919. 
llclridoo, Silvers, ard AlDltctt; (6?) In 1919 rsported an errtensive 
study 01 derris as an insscticidc. The following is a list of the material 
\ised and the sourcas frOifl which and through which it Wc?s secured: Powdered 
roots of a species nf De rri s, most lilcely Perri s elliptica Benth. , from the 
open market where it i^ sold as an insecticide; 'roots of D. elliptica , 
called "tuta" or "toeba" in the I>utch East Indies, from the 's Lands 
Plantentuin, Buitenzorg, Java; stemc of D. uliginosa Benth. , from C. H. 
Knowle-, Suva, ?iji Islands; stems of D. koolgibherah Baill. and of D. 
oligosperpa, from the director of the Botanical Gardens at Brisbane, 
Queensland, Australia; roots of D. scanden s Benth.; and stems and roots 
of 1), roDusta Benth., from the director of the Botanical Survey of Siopur, 
Calcutta, India. 
The authors' conclu.sions are a,s follows: Derris powder dusted 
upon insects does not pass into the tracheae, hut a lir^.ited amount of it 
may lodge in the spiracles, though never sufficiently to interfere with 
breathing. In order that the vapors and exhalation from a nicotine- 
spray solution "be effective, 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 -Qodies in order that its exhalation m.ay pass into the spiracles in 
as undiluted a condition as possible. After being dusted the insects 
seem to swallow some of the pov/der, 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 nerve tissue. 
Derris acts both as a contact insecticide and as a stomach, poison, • 
but is of no practical value as a f-umigant. Six species of derris y/ere 
tested, but only two of them (el liptica and uliginosa ) were found to be 
satisfactory for insecticidal purposes. 
The toxic principle in derris kills some insects easily and others 
with difficulty, but it usvally acts slowly and seoms to kill by motor 
paralysis. 
Derris pov/der, used as a du3t under practical conditions, was found 
to be efficient against dog fleas, chicken lice, house flies, three species 
of sphids ( Aphis rijmici s L. , A, pomi Dege^^r, and Myzus persicae Sulz.), 
potato-beetle larvae, and small fall webworms, but of no practical value 
against bedbugs, roaches, chicken mites, mealybugs, O rthezia i nsign.i Dougl. , 
red spiders, or "^he crawling young of the oyster-shell scale. Used as 
powdtT in water v/ith or without soap under practical conditions, it proved 
to be efficient against most of the aphids sprayed and also against cabbage 
worms, Autographa b rassica e Eiley, the larvae of apple da* anas, Pat ana 
ministra Drury, oak worms, Anisota senato ria A. and S. , snail tent cater- 
pillars, and potato-beetle larvae. 
