DEHYDROCHLORINATION AND DDT-RESISTANCE IN CULEX MOSQUITOS.

The mechanism of resistance to DDT was investigated in Culex mosquitos to ascertain whether it was associated with detoxication to DDE as in houseflies and Aedes aegypti. Resistant larvae of C. tarsalis were found to effect this dehydrochlorination, whereas the susceptible larvae did not; resistant larvae of C. fatigans completely converted all the absorbed DDT to the metabolite DDE. Enzyme assays in vitro showed that the resistant C. fatigans had 10 times the dehydrochlorinating activity, and resistant C. tarsalis four times the dehydrochlorinating activity, of their susceptible counterparts. The DDT-dehydrochlorinase enzyme of C. fatigans resembled that of Aedes aegypti more than that of the housefly, though differing from it in at least one respect.