BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 
PARASITES OF TRUCK CROP INSECTS 
During the summer of 1939 a total of 9,500 puparia of Meigenia 
rnutabilis (Fall.) (formerly referred to as fomVis Meig.) and 1 < .<vr> 
host larvae containing this parasite were imported from France for 
use against the asparagus beetle. From this material 0,550 adult 
flies were reared and liberated in infested fields in New Jersey during 
the period from late June to August. Excellent establishment was 
secured, but overwintering conditions were apparently adverse, as 
none of the flies appeared in the field the following spring. 
A consignment of 1.800 puparia of Lydinolydella metalhca Towns., 
a parasite of the larvae of the Mexican bean beetle and other species 
of EpUachna^ was forwarded from Brazil for test against the bean 
beetle. . . 
The survey of the pea moth and its natural enemies m France 
was completed at the end of the 1939 season. Five species of para- 
sites were found to attack it, although only two, Ascogaster quadri- 
dentata Wesm. and Ghjpta haesitator Grav., were of any importance. 
Field parasitization ranged up to 40 percent, with an average of less 
than 20 percent, 
EFFECT OF CHEMICAL CONTROL METHODS ON POPULATION OF NATURAL 
ENEMIES 
Activities under this project continued on the same basis as last 
year. The work on fungous diseases of scale insects in Florida was 
completed and the Orlando station closed. The staff was transferred 
to the Whittier, Calif., station to expand the work on the series of 
citrus pests under investigation there. 
Results of the biological-control experiment on the codling moth 
in West Virginia, which is being conducted cooperatively with the 
Division of Fruit Insect Investigations and the West Virginia Agri- 
cultural Experiment Station, were not so favorable as in preceding 
years, owing mainly to a very light setting of fruit in the biological- 
control orchard as compared with that which received the standard 
spray treatment. The percentages of sound picked fruit were 53.4 
and 71.7, respectivel}-, for the two orchards. A predaceous thrips 
w:is much more abundant in the biological-control orchard and is a 
very effective predator upon the codling moth eggs. 
Experiments on the citrus red mite in California showed that the 
infestations following treatment with oil-derris were higher than 
they were in untreated groves, and the predator populations were 
lower. Black scale populations increased more rapidly after spray- 
ing with oil than after fumigation, and parasitization was higher in 
the fumigated groves. Extended tests were made on the effect of 
various insecticides used against citrus pests upon the different stages 
of their natural enemies. Both oil sprays and cyanide fumigation 
were very destructive to the predaceous mite w hich preys upon the 
citrus red mite. Dinitro dust was exceptionally destructive to the 
immature stages of all red mite enemies. Both cyanide fumigation 
and oil sprays were slightly detrimental to the immature stages of 
parasites of the black scale, while cyanide killed a higher portion of 
the unemerged adults. Fumigation of the yellow scale parasitized 
bv Compendia bifasciata How. revealed that a dosage sufficient to 
kill practically all scales permitted the survival of large numbers 
