- B.5 - . 
and biologicc-^.l studies of insecticidal substances dprived fron rctr-n-me- 
containing plants, Hotenone-corit^ining plants, e.g., species of Derris , 
Loncho carpus , Tephrosia , and Mudulea , arp essentially contact insecticides: 
therefore the present work has "ber.n devoted to evaluating only contact 
action. An improved imniersion method for laboratory testing of contact 
insecticides is described and the rigid technir^ue necessary is detailed. 
The effect on the resistance of A, advena to a derris insecticide of vary- 
ing the time of immersion, the age of the insects, the temperature, pna the 
humidity before, during, and after immersion is illustrated and shows the 
necessity of controlling all these factors. Results with a standard derris 
insecticide were given to show the great accuracy that can be obtained by 
the new method; that the same result v/ith the same insecticide can be re- 
peated from day to da.y; and that two workers using the sarr.e insecticide 
have obtained identical results. 
Laemophloeus turcicus G-rouv. 
The adult is very susceptible to derris. — Craufurd-Benson (PO) in 193S, 
Oryzaephilus mt^rcator ( Fauv . ) 
The adult is v-^ry susceptible to derris and is a suitabl--; tost insect 
for evaluating d'-rris pre-narations in the laboratory. — Craufurd-Benson 
(qO) in 193g, 
Qryzaephilus surinamensis (L. ) , the sav;-toothed grain beetle 
The adult is very susceptible to derris and is a suitable test 
insect for evaluating derris preparations in the laboratory. — Craufurd- 
Bcnson (^O) in 1932. 
Used by Martin ( 273 ) ^^ 19^0 in determining the relative toxicities 
of different species of derris. The insects wer^--- reared in a constant- 
temperature and humidity room (27° C. and 70 percent relative humidity) 
on sultanas and flaked maize. Spraying trials, using for each concentra- 
tion a 5~f<^l^- replication of 25 insects, were carried out in an apparatus, 
devised by C. Jf'ottcr, a description of which will be published later. 
The apparatus is designed to give, a uniform deposit over an area of approx- 
imately 70 cm/^, pnd is suitable for use with ouickly moving insects. 
Trir'ls were first carried out using the resins suspended in a mediam of 
0.5 percent of sulfonated lorol containing 10 percent of alcohol. The 
deposit used was of the order of 1,2 mg. per scuare centimeter. The in- 
sects aft~r being sprayed were returned to the constant t-rnperature room 
and examined 2^+ hourc later. The percentaf!;es of badly affocted, moribund, 
and dead insects vrere taken in assessing the results. 
Curculionidae 
Amorphoidea lata Motsch, 
All adults on cotton plants in one o" th<-" plots at th--- Philipvin--' 
Carnival ExposHion were killed by a derris-gawgaw dust, — Butac (62)in 
193S. 
