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Background and Objectives: The current study represents the first part of a Ph.D. research project conducted at The University of Guelph, Ontario, Canada in co-operation with the University of Babylon, Hilla – Iraq. The main objective of this part was to estimate the acute toxicity (LD 50) of clothianidin, imidacloprid (neonicotinoids), and carbaryl (Crabmeat) to honey bees. Method: The Three insecticides have been blamed for the colony collapse disorder (CCD) crisis, newly emerged adult bees were challenged orally and topically with a serial of doses of the three insecticides. Determination of the LD50 of each insecticide revealed that clothianidin was the most toxic insecticide to bees in oral and topical applications compared to the other two insecticides. The findings: The oral LD50 values were 0.004, 0.15, and 0.36 μg/bee for clothianidin, imidacloprid, and carbaryl respectively. The topical LD50 values were 0.034, 0.085, and 0.24 μg/bee for the three insecticides respectively Data were statistically analyzed by probit analysis using the US Environmental protection Agency statistical program (version 1-5). [ABSTRACT FROM AUTHOR]