Certain plant parts used as spices possess insecticidal potential against insect pest of crops and homes.  The effect of Xylopia aethiopica (Negro pepper) and Piper guineense (West African black pepper) at 0.5g (2.5%) and 1g (5%) powdery formulations were employed as contact against 10 pairs male and female Callosobruchus maculatus introduced seperately into rearing jars containing 20g each of Ife Brown and ITB45-2246-4 cowpea cultivars under laboratory conditions, 25-30⁰C and 80-98% R.H. The experiment was carried out in a completely randomized design and data was analysed using analysis of variance. All rate of treatments showed significant difference in oviposition, hatchability, larval and pupal mortalities when compared to the untreated seeds. Leaf powder of Xylopia aethiopica and Piper guineense at 1g/20g caused significant reduction (P < 0.05) in the number of eggs laid on IT845-2246-4 (37.25) and Ife Brown (44.25) when compared to control (59.87). Developmental rates of C. maculatus also differed significantly between treated and untreated seeds and between Ife Brown and ITB45-2246-4 cowpea cultivars.  The result of this work showed that P. guineense is preferable to Xylopia aethiopica at all rates of formulation by the bruchid. The use of these botanicals will assist peasant farmers in overcoming the menace of C. maculatus to stored cowpea.