Acquired Resistance to Phenothiazine by Larvae of the Primary Screwworm

Abstract

Repeated rearing of larvae of the primary screw-worm, Cochliomyia americana, on media containing toxic concs. of phenothiazine in which surviving larvae were saved in each generation resulted in the development of a strain of the primary screwworm having a high degree of tolerance to phenothiazine as compared to the original strain. After 8-9 generations of exposure to media containing highly toxic concs., parallel toxicity tests showed the number of survivors of the resistant strain to be 18 times that for the regular strain.