50 ANNUAL BEPOBTS OP DEPARTMENT Of I CUBE, 1 
i In the two tests. Tv. othirds of the bees killed by parathion 
I ii: the apiary, whereas two-thirds of the deaths from ehlordane 
andmosl of those from DDT and toxaphene occurred in the field. 
A in the number of bees visiting an alfalfa field was noted 
after the use of I >1 >'l . ehlordane. itnion. Mortality accounted 
rely for this decrease in fields dusted with ehlordane or parathion, 
but wnere DDT was used a Blow repellency seemed to exist, which 
limited the numl er of deaths by reducing the number of visitors to 
the field. 
Bees poisoned by ehlordane or e hexachloride ; slug- 
gish an<l quiet with occasional spasms, similar to their normal resp 
to low temperatures. In contrast, bees poisoned by DDT sh< 
characteristic immediate tremors and greatly increased activity fol- 
lowed by paralysis. Death from DDT came more quickly than from 
t lie ni her i wo insect icid< 
The lethal contacl dosage of DDT per bee was found to be about 
o l v microgams and that of ehlordane about 6 to 10 micrograms. 
In cage bests with different concentrations of DDT the mortality 
depended on the amount of DDT present per bee. A decline in 
mortality was observed when the temperature was above v,) T\. the 
temperature range tested being 71. .v to s "»". There seemed to be 
some tendency for the mortality to decline also with the humidity, in 
the range 61 to 92.5 percent, although this wa - not clearly established. 
Spraying colonies with ehlordane did not kill all the bees. In ono 
test, while a red clover field in bloom was being treated for gi 
hopper control, ehlordane was sprayed freely over the hives of three 
small colonies. Some bees were on the outside of the hive at the 
time. Nearly all the bees were affected and many died, but the 
colonies survived in a weakened condition. Two bumble bees col- 
lected in the treated area and caged on the day after the spraying died 
within 3 days, but a third lived more than 17 days. Caged solitary 
bees died the day after they were collected. 
Norma melanderi) a wild bee pollinator of alfalfa, was found to 
be affe< ted by I >DT applied while al falfa was in bloom. A S-percent 
dust was applied early in the morning at 20 pounds per More 
than half the female bees nesting in the area visited the alfalfa on 
the same day. Although the dust seemed to be moderately repellent 
for a few hours, more than 2 percent of the bees nesting in sample 
areas were found dead at their nest i es and about 15 percent 
of the nests became inactive, apparently as a result of the treatment. 
Spraying or dusting for insect control while crops are in bloom should 
be avoided wherever possible. If necessan to save the crop, insecti- 
mould be applied at a time of day when the bees are ina< 
Hone) Beea Bred for Resistance i<> imerican FouObrood 
The progeny of two of the lines of honey bees showing marked re- 
ce '" American foulbrood in L947 were 100 percent resistant to 
tlii- disease in L948. ()iu' line, however, showed considerable lack of 
