DEVELOPMENT OF PHEIDOLE-MEGACEPHALA (HYMENOPTERA, FORMICIDAE) COLONIES FOLLOWING INGESTION OF FENOXYCARB AND PYRIPROXYFEN

Laboratory-reared Pheidole megacephala (F.) colonies were fed 2% pyriproxyfen (Sumitomo S-31183) or 2% fenoxycarb, ethyl [2-(4-phenoxyphenoxy)ethyl] carbamate, in soybean oil. Queens in colonies treated with pyriproxyfen laid significantly fewer eggs than controls 2 wk after treatment. Oviposition ceased in all pyriproxyfen-treated queens at 6 wk after treatment, with no recovery during the 15 wk of the study. Brood volumes in pyriproxyfen-treated colonies declined after 2 wk because of pupal death. No brood was found after 4 wk. Fenoxycarb-treated queens laid significantly fewer eggs than controls after 2 wk. Fenoxycarb-treated colonies shifted caste differentiation from workers to males at 3 wk after treatment. At 5 wk, 90% of larvae were male; the remaining 10% developed into intercastes.