Effects of prey density and adult predator size on food consumption and oviposition were evaluated in an aphidophagous ladybird beetle, Menochilus sexmaculatus (F.), from tropical Asia. Both the functional response and reproductive numerical response showed an upper asymptote at 40 adult Aphis craccivora Koch/female/150 cm². Proportions of aphids consumed and eggs laid by female beetles were highest at lower aphid densities, i.e., five or 10 adult aphids. Ratio of eggs laid to aphids consumed, by dry weight, was highest at the lowest aphid density, i.e., five adult aphids. Larval food supply significantly influenced the size of adult females. After 24 h, smaller females consumed significantly fewer aphids and laid fewer eggs in comparison to larger females, but conversion efficiency from food to eggs remained the same irrespective of the difference in adult size. Results suggested that this ladybird species exploit prey efficiently at low density.