28 Gz 
as 85 to 95 per cent, and of the purple scale, 60 per cent. When lead 
arsenate, cryolite, or potassium aluminum fluoride were sprayed on 
citrus trees the percentage of living white fly pupae at the end of eight 
months was from one and one-half to five times as great as on unsprayed 
plots. With copper compounds the white fly pupae were five to ten times 
as numerous as on the check plots. With Bordeaux mixture the fungous 
control was cut to 45 to 50 per cent. In the case of the purple scale, 
copper compounds doubled the increase of the scale; lead arsenate, 
cryolite, and aluminum fluoride were without effect either on fungus 
or on scale: and Bordeaux mixture reduced the fungus control of the pur- 
ple scale to 20 per cent. 
vacuum.~~A. C, Mitchell, of the Mediterranean fruit fly laboratory at 
Honolulu, T. H., has been studying over a considerable period the effect 
of vacuum on Mediterranean fruit fly adults and larvae. He makes the 
following comment on his experiments: "As the flies and larvae have open 
tracheal systems, the pressure must adjust itself rapidly throughout 
the bodies of the insects. If death were due to the reduced pressure, 
there would be little likelihood of survival for such long periods of 
time as were noted. The comparison of adults exposed to 1 cm and 2 cm of 
mercury showed that the survival period at the lower pressure was rough— 
ly half that at the higher, and the oxygen tension at 1 cm was of course 
half that at 2 cm. These various observations lead to the conclusion 
that it is not the reduction in pressure so much as the lack of oxygen 
that is the cause of death. And another conclusion would be that lar- 
vae have lower oxygen requirements than adults, at least in the last sta- 
ges (as the larvae tested were in the third instar, and nearly ready to 
pupate). It is expected that it will be possible to check this conclu— 
sion directly by means of respirometer readings." 
Promising poisons for fruit flies.—-Among the numerous poisons for 
use in baits for various species of fruit flies tested by James Zetek, 
in charge of the Canal Zone laboratory, tartar emetic and borax have 
been found promising. Of the two materials tartar emetic (tartrate of 
antimony and potassium) is much more rapid in its killing effect. Mr. 
Zetek says: "At the rate of 8 pounds to 100 gallons of water, with 5 
gallons of molasses, all of Anastrepha fraterculus Wied. died in 24 
hours. Using only half the amount, at least 4 full days were necessary 
to kijl all adults. Molasses at the rate of 5 per cent seems to be suf-— 
ficient. I could note no effect of the spray on either mango or citrus 
trees." 
Oriental fruit moths not caught after dark.--L. F. Steiner, Corne— 
lia, Ga., reports that "Preliminary observations indicate that most moths 
are captured by traps during the short period preceding darkness in the 
evening and for a few hours in the morning, if weather conditions are 
favorable." 
sults of temperature experiments at the Mexico City laboratory, A. C. Baker 
