Millettia pachycarpa Benth. (family Fabaceae) is a well-known medicinal plant in the traditional systems of Chinese and the Mizo tribes of India. One of its many uses is as an insecticide. The extract of the root bark was examined for larvicidal and ovicidal activities against the dengue vector mosquito Aedis aegypti Linn (Diptera: Culicidae). The early fourth instar larvae were treated with serial concentrations of the plant extract (viz. 6.25, 12.5, 25, 50, 100 and 200 mg/L) continuously for 24 h. Data indicate that the plant extract exerted profound lethal activity (LC50 = 98.47 ppm at 24 h) on the larvae. For evaluation of the ovicidal activity, concentration was increased until when there was complete inhibition of egg hatching. Mean percent hatchability of the eggs was noted at different time intervals from the freshly laid eggs up to 24 h old. At high concentration (200 mg/L) of the plant extract, there was complete inhibition of egg hatching (100% non-hatchability). The observation also indicated that the percent hatchability was inversely proportional to the concentration of the extract, and directly proportional to the age of the eggs. Therefore, the extract of M. pachycarpa root bark exhibited significant mosquitocidal activity against A. aegypti.
