Evening star. [volume] (Washington, D.C.) 1854-1972, 1953-02-13
Some Flies Taking To
DOT Like Garbage
It's Not All Resistance;
Many Too Luzy to Eot Poison
By Thomas R. Henry

Some houseflies have developed q
resistance to the supposedly deadly in
secticide, DOT. more than 5,000-fold
greater than normal.
This was reported to q National Re-
search Council conference by DR.. Ralph
B. March Of the agricultural expert.
ment station at Riverside. Calf.
At the same time, DR.. March reported.
the California flies now are resistant to
at least 10 other poisons Of the general
DOT class, some Of them considered
much more deadly. The phenomenon
now has reached the point where it Is
practically useless to employ most in
secticides for fly control.
Southern California. with its nearly
tropical climate, allows practically year.
round breeding Of housefies. This gives
q better opportunity for resistant gen.
erationS to make their appearance.
DOT. Mr.. March reported to the con-
ference. first was used there in 1916.
shortly after its introduction for civilian
use. At first it seemed to work like a
charm. But by the spring Of 1919
many complaints were received by the
experiment station Of the Ineffective
ness of the poison. Investigations in
the field showed that in several areas
wild flies had appeared. specifically no
different than any others. which could
stand about 800 times the supposedly
effective dose-that is, the concentra-
ton of poison that would kill at least
half of given fly population.
New Chemical Tried.
A new chemical Of the same general
class, benzene hexachloride, was tried.
It had been hailed as the super-killer.
but within year failures were reported.
A resistant population had started. The
experience has been the same. DR..
March said, with the poisons OF the
general DOT family - tethoxychlor.
lindane, chlordane. toxaphene, aldrin
and, dieldrin. all once held as possible
saviors. Much the same phenomenon
has made it's appearance among South
ern California mosquitoes. Mosquito re-
sistance first was observed in 1949 and
evidence of growing resistance has been
accommodating ever since. .,.
This California experience was prob
ably the most striking reported at the
National Research Council conference
on the reasons for the growing resist
ance to insecticides which apparently
Is taking place all over the earth. 1t
may be a matter of development OF
hereditary resistance to the poison It
self. although this, it was stressed, prob
ably is too simple an explanation. One
explanation advanced was that the
hereditary change might be In the
behavior of the insects, rather than
altogether in their ability to Withstand
poison. This was illustrated by DR..
George c. Decker Of the University OF
Illinois, A farmer, for example. reported
an enormous increase in the number
of stable flies in his barn at time OF
year entirely out of season for these
insects. A university investigator found
that they we're not stable flies but
ordinary housetiieS. But. instead OF
moving about as housef1ies ordinarily
do, these flies 'Just sat-" They were
survivors that hadn't been killed by
DOT Just because they lacked the
energy to come in contact with it.
Lazy Flies in Italy. ..,
The same phenomenon Of lazy flies,
which owe their survival to apparently
inherent laZineSS, also was reported
from Italy when DDT resistance first
appeared. <.., s.at,..sy-
Resistance, it was stressed, appar-
emily is developed in two Jumps. 1t
develops for few generations in a
steplike fashion, perhaps reaching for
an insect population approximately 100.
fold normal. Then big Jump comes
quickly and the bugs show resistance
1000 or more times that of popula-
ton where there is no resistance. 1t
may be, some who attended the con-
ference held, that several kinds OF
resistance develop in different family
lines of an insect population. and that
at some point all these lines converge
to produce poison-proof bugs. Much
the same phenomenon has been sus-
pected in the development of resistance
to sulfur drugs and biotics by bacteria.