The toxicity and biochemical of the two insecticides methomyl 20% SL and diazinon 60% EC used as bait or contact poisons were studied against different ages of Monacha obstructa. The LC₅₀ and LC₉₀ values of each compound were determined for the different ages of M. obstructa.Different concentrations of each compound were tested against M. obstructa using baiting and contact thin layer film (TLF). Mortality percentages were recorded 24, 48 and 72 hrs., after treatment. Methomyl was toxic used as poison contact for all tested ages, while methomyl was moderately toxic when it was used as poison bait on all different ages (1, 3, 6, 9-12 and over 24 months). Methomyl and diazinon were toxic in high concentrations as contact than bait gave highly mortality percentages in adult and (over 24 months) than (one month, three month and six month) after 72h from treatment. Regarding the contact method, diazinon was toxic to the three-month and old individuals. The repellent effect of the two insecticides methomyl and diazinon against (one month, three month, six months, 9-12 month adult and over 24 months old) different ages of M. obstructa were studied and medium repellent different ages while vice versa occurred in case of diazinon, as it was repellency at the same ages. The biochemical response of the different ages of M. obstructa treated with LC₅₀ of methomyl and diazinon compounds, whereas AchE response of the three and six months ages differed with the all ages to both compounds. The response of LDH and AST variation to each age of M. obstructa. On the other hand, effect of two compounds on total protein and total lipid similar in most ages except six month and old ages reduced after 72 h, treatment.