Evidence for differences in mode of action between two related carbamate insecticides

Carbaryl (1‐naphthyl N‐methylcarbamate) and its N‐acetyl derivative have been compared in respect of toxicity (LD50), rates of kill and anticholinesterase activity in vitro and in vivo, using the honeybee as test organism. Results obtained indicate that carbaryl does not act solely on brain cholinesterase. Alternative suggestions are discussed, together with observations supporting the idea that the N‐acetyl derivative iS metabolised to a more potent cholinesterase inhibitor.