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the materials tested than the regular colony. Although a few reversals 
occurred in the individual tests, none appeared in the final averages at 
any concentration. To obtain equal mortalities, approximately twice as 
much toxicant was required for the special stock as for the regular stock 
with DDT, chlordane, pyrethrum, and rotenone. These tests show that the 
method of selection resulted in the development of an unusually strong 
stock of flies rather than one having a specific resistance to DDT. — Wilson 
and Oakan (428). 
In tests made in southern California in 1949 against resistant house- 
flies chlordane, applied as a 40-percent wettable powder at 50 pounds per 
100 gallons of spray (approximately 2.5 percent), gave an excellent initial 
clean-up and in some cases residual action lasted up to one month. In 
other cases, however, reinfestation was very severe after one to two weeks. 
The rate of fly knockdown "by chlordane is slower than that of DDT. — March 
and Metcalf (ii). 
In samples of flies obtained from seven localities in five states 
heavy deposits of wettable chlordane and methoxychlor were nonrepellent or 
even slightly attractive. Eespraying of two "barns with chlordane emulsions 
and two with suspensions of methoxychlor provided a high degree of control 
for several weeks. — King and Gahan ( 263 ). 
Flies from 6 barns in New Jersey which had been sprayed with DDT ex- 
hibited resistance in laboratory tests to technical DDT and p^'-DDT 
residues of 144 mg. /square foot. All these resistant flies were killed in 
tests using residues of chlordane. — Eansens et. al. (204). 
Specimens of a wild population of house flies that had survived re- 
peated residual-type applicaions of DDT in Ellenville, New York were cap- 
tured and offspring were cultured in the laboratory through three genera- 
tions. Tests were made to determine whether this line of flies was resist- 
ant to DDT and, other new insecticides as compared with a laboratory line of 
flies whose ancestors had never been exposed to these insecticides. The 
results of these tests showed that flies of the Ellenville line were highly 
resistant to DDT and related compounds, but showed no resistance to certain 
unrelated chemicals. The results of the tests with technical chlordane are 
as follows: A total of 18 tests were made in which flies were exposed for 
2 hours, 1 hour, 30 minutes, or 15 minutes to surfaces to which 144, 100, 
70, or 14.4 mg. of the active material had been applied per square foot of 
surface. All flies exposed to surfaces to which the three larger concentra- 
tions had been applied were killed as were those exposed for 1 hour to a 
surface to which 14.4 mg./ square foot had been applied. The percentages of 
mortality of flies of the laboratory and Ellenville lines exposed to the 
latter surface for 30 minutes were 100 and 94«4, respectively, and for 15- 
minutes exposures they were 95.6 and 60, respectively. The comparative 
rates of mortality for all tests in which 387 flies of the laboratory line 
and 459 of the Ellenville line were used, were 99.7 percent for laboratory 
flies and 98.5 percent for Ellenville flies. — Barber and Schmitt (26). 
In another series of tests with technical chlordane against these 
same 2 lines of flies, five tests were made in which flies were exposed 
