The essential oils of chamomile; Chamomilla recutita L., rosemary; Rosmarinus officinalis L. and peppermint; Mentha piperita L. were tested under laboratory conditions for their ovicidal and biochemical activity against the eggs of greater wax moth, Galleria mellonella L.The incubation periods, hatching periods and hatching percentages of the eggs treated by the three oils using spraying technique were significantly retarded at the four concentrations  1%,2%,4% and 8%. Generally, the maximum ovicidal activity was recorded at 8% concentrations and the peppermint oil showed marked activity against the eggs of greater wax moth. The longest incubation period (15 days), the longest hatching period (6.67days) and the highest inhibition of hatchability (5.07%) achieved with peppermint oil treatment, followed by rosemary oil (13.67 days, 5.33 days and 18.25%) then chamomile oil (9 days, 5.67 days and 32.45%), respectively. The chemical constituents of the three essentials oils were analysed using gas chromatography (GC). Bisabolol oxide a (43.76 %) and bisabolol oxide b (16.11%) were the major components of chamomile oil whereas, camphor (23.56 %), 1,8-cineole (17.86 %) were for rosemary oil and menthol (47.38 %), menthone (29.99 %) for peppermint oil. Present study demonstrated disturbance in total soluble protein, total lipid contents and inhibition the activity of acid phosphatase and phenoloxidase.