-36- 
Fransen ( lAl ) -in 1939 reported the results of investigations in 
Holland on the -most economical employment of contact dust insecticides. 
.The apparatus used for ascertaining the minimum lethal dosages .is des- 
cribed. Tests were mace on larvae in different stages of development. 
Ten tiroes as much rotenone was necessary to kil 1 overwintered larvae 
1.2 cm. long as to kill first instars 0.35 cm ,/ 1< ¥n s 1 9 4-0 Fransen ( U2 ) 
reported that the best results were obtained by dusting with pyre thrum 
against larvae in theaarlier insters and with derris against the older 
ones, but crushing the nests is still considered the most effective 
control measure. 
Notolophus antiqua (L.), the rusty tussock moth 
Gimingham and Tattersfield ( I6l ) in 1928 reported that in labor- 
atory t~ sts extracts of the stnms and roots of black and white haiari 
and of the leaves of Tephrosia vogelii were extremely repellent to 
larvae of this species. , Soap, 0.25 percent, was added to these ex 
.tracts. Even at high dilution (l part plant material to LOO parts water), 
the sprayed foliage remained uneaten and the larvae died of starvation. 
A.n alcoholic extract of the root o f Tephrosia macropoda was 
sprayed on the larvae and had considerable contact insecticidal value. 
Alcoholic extracts of black haiari ( Lonchoc-rpus sp.) were toxic to ■ 
the 1 month-old larvae. — Tattersfield and Gimingham ( 401 ) in 1932. 
l\ product containing 12 percent of powdered Lenchocarpus nicou 
root (6-percent rotenone) and. 88 percent of talcum mitigated ( Orgya ) 
. T otolophus antiqua (L. ) on apple and plum, according to Etablissements 
Rotenia in a letter to R. C. Roark in 1938. 
• Porthesla scintillr.ns (Walk.) 
P. sericea (Wileman) 
P. taiwana Shir. 
Sonan ( 378 ) in 1927 reported that spraying with derris and soap 
proved very effective -gainst those species infesting tea plants in 
Formosa. 
Porthetria disp-^r (L. ), the gypsy moth 
See also Tragardh ( 416 ) under Pa noli s grisoovariegrt- , on page 92, 
feis (477) in 1931 reported that the larvae were killed more 
quickly when dusted with Polvo on the ventral side than when dusted 
on the dorsal side. Polvo repelled fourth and fifth instars. 
Potts ( 3,30 ) in 1935 reported that promising results were obtained 
with derris as a stomach poison against a number of insect, species (in- 
cluding the gypsy moth) when an oil adhesive such as 0. c to 1.5 percent 
of castor oil, fish-oil, or linseed oil was added to the spray mixture. 
were 
Trapprnann and Nitsche (417) in 1935 reported that rotenone dust: 
not effective against last instars after 8 days. Dosage was 
