DISTRIBUTION OF 14 C-LABELLED CARBOFURAN AND DIMETHOATE IN ROYAL JELLY, QUEEN LARVAE AND NURSE HONEYBEES

Abstract

When sublethal levels of the 14C-labelled systemic insecticides carbofuran and dimethoate were fed in sugar syrup to caged nurse bees (NB) in the laboratory, radioactivity was detected in both royal jelly (RJ) and queen larvae. Although 14C-dimethoate was provided in syrup at lower concentrations than 14C_carbofuran, higher levels of radioactivity were found in larval food and larvae with the former. In order to understand more fully the pathway of systemic insecticide into brood food, a distribution study of 14C_insecticidc within NB was conducted. When individual NB consumed sublethal levels (< 1/ 30 x LD50) of 14C-insecticide, radioactivity was found to be largely confined to parts of the digestive system, including the honey sac (HS), with very little in various glands of the head and thorax. Results suggested that contamination of RJ occurred with the delivery of contents from the HS, rather than by secretion from the head glands responsible for the glandular component of larval food.