Grasshoppers are ecologically significant because many animals consume them as a major protein source and thus any change in their population dynamics may have detrimental effects on an ecosystem. This study evaluates effects of mercury (Hg² ) on the developmental periods of different instars of a common short-horned grasshopper, Oxya fuscovittata (Marschall). Newly hatched nymphs were fed foods treated with three sublethal concentrations of HgCl₂ i.e., dose 1 (d1): 20 mg HgCl₂/ kg dry weight in oats, dose 2 (d2): 40 mg HgCl₂/ kg dry weight in oats, and dose 3 (d3): 80 mg HgCl₂/ kg dry weight in oats, until they reached the adult stage. The experiment was conducted for two consecutive generations (F1 and F2), tested in the same way for the same variables, in order to observe if there is any additional adversity in the latter generation. As HgCl₂ concentrations in food increased, the Total Rearing Time (TRT) for each instar significantly increased, whereas survival, adult body weight and adult life span significantly decreased. The results for the F2 generation almost always showed more severe effects than those of the F1 generation.