29 
Tanaka (91) in 1927 reconmended a derris soap spray for the control 
of the older larvae of the ITotodontid Lrymonia manleyi Leech, 
T\7inn (96) in 1927 reported on mosquito control at Ottawa, Ontario, 
Canada, The derris was dusted on the -/ater surface at the rate of approxi- 
mately- 3 2"0^^ds per acre. The larvae died within periods ranging from 
three-quarters of an hour to more th.an 7 hours. In all cases the larvae, 
before de:.th, became verj* feeble, lying motionless and parallel v;ith the 
surface of. the water, moving with difficulty when rudelj' disturbed. The 
pupae died more slowly than the larvae, more than 24 hoxirs sometimes 
elapsing before death occurred. 
Tests T/ere also made upon a shallow pool about ^00 square feot, 
with a grass-grown bottom. This pool contained largo numbers of lar\-ao 
of Aedos voxans Meig. A mixture of derris and French ch£ilk in the pro- 
portion of 1 part of the former to 4 of the latter was dusted just before 
sundown on the surface of the water by moans of a small hand dust gtm, at 
the rate of l-l/2 pounds of derris to the acre. The material settled 
well, foming a very satisfactory film of dust over the entire surface. 
When examined 16 hours later, a considerable proportion of the larvae 
were dead end many of the living revealed the effect of the derris in 
their sl^oggish movements. The pool was not examined again until 60 hours 
after treatment. On this occasion all ihc larvae wore dead, many floating 
on the surface of the water, 
TJalton (107) in 1927 reported further notes on the control of 
warble flies in North Wales, The killing properties of derris appear 
to be excellent. The ointment (l part of derris powder plus 2 parts of 
soft pa.raffin) is odorless, and the cost is low (about 2-1/2 pence per 
ounce) in experimental amounts. On the other hand, the ointment was 
found to be much more difficult to apply, and olive oil was utilized, 
the ointment then consisting of 1 part of powdered derris, 1 part of 
soft paraffin, and 1 part of olive oil. This improved the texture and 
rendered application easier. 
Watanabe (108) in 1927 recommended spraying the young growth of 
cruciferous vegetables with derris to combat Hellula -undalis F. (Pyralididae) 
in Japan, 
Trappraan (94) in 1927 gave a short account of derris. A formula 
for a derris spray is 1 kilogram of finely pov;dered derris powder, one~half 
kilogr;ar.i of soap, and 100 liters of water, Derris powder may be added to 
a load arsenate (1 percent) and soap (0.3 percent) spray for use on young 
tobacco plants. 
1928 
Thompson (93) in 1928 tried derris in poison bait against leather 
jackets in South Wales and foimd that, although it did not give as good 
results as the paris green bait, it is obviously of definite insecticidal 
