Effect of Chlorcyclizine, Aminopyrine, or Phenobarbital on Carbaryl Metabolism in Alfalfa Leafcutting Bees 1 , 2

Abstract

Alfalfa leafcutting bees, Megachile pacifica (Panzer) (= rotundata Fabr.) were fed, for 72 h, either chlorcyclizine, phenobarbital or aminopyrine dissolved in an aqueous 25% sucrose solution. The bees were then topically treated with one μg of radioactive carbaryl per bee and the distribution of carbaryl and its metabolites was studied after 4 hours. Carbaryl was most persistent in bees fed aminopyrine. Phenobarbital feeding had no effect on carbaryl persistence in either sex. Chlorcyclizine reduced carbaryl persistence in ♂ bees but had no effect in ♀ bees. Aminopyrine feeding reduced carbaryl metabolism in ♀ bees and eliminated it in ♂ bees except for the production of a single water soluble metabolite. Analysis of the results suggested that carbaryl tolerance in the bees depends upon metabolic degradation of carbaryl and is correlated with removal of the insecticide from the lipophilic fraction of the bee's body.