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tall izat ion method. The rotenone content must therefore be given first 
consideration in rating derris root. In derris root containing a suff- 
icient amount of rotenone (4 percent or more) the quantity of ether 
extract is of no consequence in respect to "biological effectiveness, 
hut ^'ith roots ^ith lo^ rotenone content (under 2 percent) and' high 
etkar . extract, the latter is a factor in the effectiveness. 
De Bussy et al. (57) and also Van der Laan (244) in 1936 reported 
that this species is sensitive to derris dust. », 
Klinger ( 237) in 1936 reported that larvae of this species had 
been used to test the effect of rotenone dusts and sprays but no 
results ••'ere recorded. 
A product containing 12 percent of pondered Lenchocar'pus nicou 
root (6 percent rotenone) and 88 percent of talcum killed this spe- 
cies on pear, according to Etablissements Rotenia in 1938, in a letter 
to R. C. Roark. 
The Koloniaal Instituut of Amsterdam ( 241 ) in 1938 proposed spec- 
ifications for derris root, derris ponder for spraying purposes, and 
povdered-derris mixtures. The moisture content of the root and of 
pov'ered root for spraying purposes must not be over 10 percent. The 
fineness of the latter material must be such that 90 percent "-ill pass 
a 75-mesh sieve. The pondered mixtures must be made "-ith a neutral 
filler, the maximum moisture content should be 2 percent, at least 90 
percent must pass a 125-nesh sieve, and the density must be between 
0.6 and 1.2. The following materials "-ere suggested as carriers: 
Diatomaceous earth (density 0.65), Kaolin (density 0.83), talc (density 
1.12), and gypsum (density 1.33). Derris ponder of a fineness such 
that 90 percent passes a 125-mesh screen has a density of 0.56. During 
1937 derris preparations containing 1 percent of rotenone "'ere used in 
the Netherlands in combating this species. 
At a meeting of the Netherlands Entomological Society in 1938, 
Polak ( 329 ) criticized the use of a derris dust against larvae of this 
species attacking trees in Amsterdam. He argued that the larvae 
'"ould be shielded by their '« r ebs against the dust, that many harmless 
species would be destroyed, and that control «>ould best be obtained 
by means of hymenopterous parasites. Diakonoff replied that derris 
greatly red.uced the ultimate number of pupae ant. adults. 
Fransen (141 ) in 1939 reported, the results of investigations in 
the Netherlands on the most economical employment of contact dust in- 
secticides. The apparatus used for ascertaining the minimum lethal 
dosages is described. Tests "-ere made on larvae in different stvres 
of development. Fifty times as much rotenone ^as neceesiry to kill 
the largest larvae as to kill the smallest used (3.0 and 0.4 cm. in 
length, respectively). The author concluded that for a giver, insec- 
ticide there is no fixed relation between the quantities necessary to 
control the larvae of this in different stages of development, and 
still less between the necessary quantities of the active co^ponrnts 
of the various insecticides and a given developmental stage of any 
group of insects. The susceptibility of the larvoe may vary, orlng to 
internal causes and -'•eather conditions. Temperature did not greatly 
