الفهرس 
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Abstract
Bioassays were conducted to study comparative and selective toxicity of commercial formulation of the neonicotinoid insecticides acetamiprid and imidacloprid against Bemisia tabaci (Genn.) and Spodoptera littoralis (Boisd) using leaf dipping technique as well as Apis mellifera by orally mixing with food media. Based on the obtained LC50 values, acetamiprid was more toxic to the tested adult and nymphal stages of B. tabaci than imidacloprid. The adult stage was more susceptible than nymph. Acetamiprid showed higher toxicity to eggs, 2nd and 4th instar larvae of S. littoralis than imidacloprid. Eggs were more susceptible than the larval instars, and the 4th instar larvae were the least susceptible. Acetamiprid at a field rate caused 3.33 % mortality to honey bee with no symptoms of toxicity, whereas a field rate of imidacloprid gave 90% mortality and obvious symptoms of poisoning. Total protein, total carbohydrates, total lipids, alanine aminotransferase activity (ALT), aspartate aminotransferase activity (AST) and alkaline phosphatase activity (ALP) and acetylcholine esterase activity as well as the metabolizing enzymes cytochrome P450 monooxygenase and glutathione-S-transferase were monitored in B. tabaci, S. littoralis, A. mellifera and rat after 24 hours of acute exposure to the test compounds. The results revealed that the efficiency and selectivity of neonicotinoid insecticides are related to the chemical group of the compound as well as the type and developmental stage of the insect. The toxicity and selectivity of the cyanoguanidine neonicotinoid, acetamiprid and the nitroguanidine neonicotinoid, imidacloprid are based on their chemical structure and metabolic pathways and seems to represent a species-specific feature. This is indicated by significant alterations of the values of total proteins, carbohydrates, lipids contents and enzymes specific activity of key enzymes in the exposed organisms.