A set of experiments was conducted to determine the dietary clothianidin exposures that cause prepupal mortality in the absence of other adverse effects. Monarch larvae were raised from hatch to pupae on clothianidin contaminated swamp milkweed plants. Larval growth, larval survival, and prepupal survival were monitored throughout the experiments in which the exposures ranged from 1.4 – 2,793.1 ng/g leaf. Exposures of 5.4 – 46.9 ng/g leaf resulted exclusively in prepupal mortality while higher exposures of 1,042.4 – 2,793.1 ng/g leaf resulted exclusively in larval mortality. An LC50 and LC10 of 37 and 6 ng/g, respectively, were estimated based on prepupal mortality.