Abstract: The development of cowpea aphid larvae was monitored on seven cowpea genotypes (IAR-48, TVu-15866, IT84S-2246-4, SAKA BABBA SATA, IT90K-76, KANANNADO and TVX 3236). The aim of the study was to determine the developmental response of the larvae as an indication of antibiotic resistance of the genotypes. Highly significant differences (p<0.01) were observed with respect to fertility, larval development, adult longevity, life span, multiplication rate and intrinsic rate of increase. KANANNADO and TVX 3236 show minimum antibiotic effects while a landrace SAKA BABBA SATA shows relatively high antibiotic effects. This result further reveals the potential of SAKA BABBA SATA as a resistance source to aphid. The reaction of IT84S-2246-4, a hitherto aphid resistant genotype, which supported higher levels of survival of the larvae relative to other known susceptible genotype IAR-48, may be an indication of the presence of a new biotype of Aphis craccivora endemic to Zaria environs, or that of the ability of insects to overcome hindrances to their survival including various forms of resistance.