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es pyre thrum. Rotenone in suspension "as also lo^er in toxicity 
then anticipated. Moreover, rotenone is kno^n to be highly toxic 
to fish end, therefore*, "£s dropped from consideration. 
Worsley ( 326 ) in 1934 reported that an alcoholic extract of 
tephrosin is ss effective against mosouitoes and similar insects 
as pyre thrum if the insects' ere actually hit with it. 
Tischler ( 275 ) in 1935 studied the mechanism of ho rr derris 
kills insects. Studies on the heart rates of various insects in- 
cluding mosauito larvae shored that the rate of pulsation was 
markedly decreased before the insects exhibited incoordineted move- 
ments. Derris inhibits oxygen utilization by the tissues and its 
detrimental effects are general rather than specific to any organ, 
Feyteud and Lapparent (87) in 1936 published the following 
formula for a mosouito spray: Cube ponder or derris ponder 10 gm. 
and pyre thrum ponder 10 gm., is macerated in 100 gm. of a. mixture 
of eoual parts of terpinolene and orthodichlorobenzene or carbon 
tetrachloride for 5 days ^ith frequent agitation, then the. product 
is filtered and a perfume is added, for example, 10 percent of 
"terpens de citronelle." 
Phillips (233) in 1938 reported a study of the effect of 13 
diets on the resistance of mosouito larvae to nicotine, rotenone, 
andphenothiazine . By feeding various diets to different croups of 
larvae it was possible to cause e variation o^ .75 percent resulting 
from nicotine enrl rotenone in the mortality -of fourth insters. The 
variation in the results from ohenothiazine was not so great, 
because in most cases the concentration used was high enough to cause 
complete mortality. In general, the better diets caused more rapid 
growth and resulted in nor'" resistant larvae. The diets did not have 
the same effect, hc-ever, with all three insecticides — in other words, 
the larvae most resistant to rotenone were not the most resistant 
to nicotine or ohenothiazine. 
Sullivan, Phillips, and McC-ovran ( 268 ) in 1938 reported that 
^n extract of the fruit of the Amur cork tree ( P he 1 1 c d e nd r on 
amurense) w?s more toxic to mosauito larvae than ^es a derris 
stend.srd containing 5.2 percent of rotenone. 
Thomssen and Doner ( 274 ) in 1938 reviewed published information 
on fly control for livestock and mentioned rotenone for the control 
of mosquito larvae. 
The Division of Control Investigations of the Pureau of Entomology 
and Plant Quarantine, U n ited States Department of Agriculture (292), 
in P e hruary 1938 reported tests ^ith derris as follows: 
Concentration Mortality of fourth instars after 
o . p . m . 18 hours ■ 
. ■ Hot expos ed Exp :>se d 
Percent Percent 
20 40~~ 11 
50 94 53 
