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TROPICAL, SUBTROPICAL, AND ORNAMENTAL PLANT INSECTS 
A. W. Cressman, of the New Orleans, La., laboratory, has completed 
a report on the rate of development of the camphor scale as influenced 
by temperature. A method has been developed for predicting, from tempera— 
ture records, the times of occurrence of different stages in the field. 
For three years the observed figures have matched very closely with the 
expected ones. 
A. W. Cressman and Mrs. L. T. Kessels have made a study of the in- 
fluence of light on the feeding rate of the Vedalia beetle. An earlier 
study by Cressman and Dumestre was made on beetles taken from the field, 
and it was found that feeding varied with the light. The present study 
is on a stock kept indoors in relatively dim light for a period of years. 
With this series the same amount of food was consumed in the dark as in 
the light. It is hoped that the studies on the Vedalia beetle may throw 
light on methods used in practical. biological control where stocks are 
reared indefinitely for distribution. 
Mr. Cressman has completed a study on the biology and control of 
the dictyosperma scale. The seasonal history has been depicted and re— 
sponse to temperature measured. One hundred per cent control was obtained 
by the use of certain 011 Sprays. 
H. H. Bliss, A. J. Haas, and A. W. Cressman have completed a report 
on soap analysis in connection with oil emulsions, recommending a method 
based on emulsifying abilities as superior to the usual method. 
The oil studies of the laboratory staff at New Orleans, in coopera— 
tion with Dr. L. H. Dawsey, assigned to the laboratory by the Bureau of 
Chemistry and soils, have concentrated on several properties, as dr@gp 
Size, drop charge, and stability. Factors conditioning drop size have been 
determined and a measure for stability has been adopted, although search 
is being made for a more satisfactory one. 
Dr. E. W. Emmart, of the laboratory at Mexico City, has completed a 
report on the egg form of the three economic species of Anastrepha, ludens, 
ee ee en ee ee 
which these species may be distinguished in the egg stage. 
Dr. H. H. Darby, of the same laboratory, has completed a report on 
the influence of temperatures on the fruit fly. This includes both high 
and low temperatures and shows figures for larvae, pupae, and adults. 
Special attention has been given to high temperatures contemplated for 
sterilization of food products. The studies, especially those on low 
temperatures, have shown that the Mexican fruit fly is a far more hardy 
insect than was heretofore supposed. "i 
W. E. Stone and C. C. Plummer, of the laboratory at Mexico City, 
have conducted a series of toxicity studies on adults of the Mexican 
fruit fly, using various copper salts, arsenicals, etc., and it has been 
found that the Mexican fruit fly is more resistant to these materials than 
is the Mediterranean fruit fly. 
