In 2010 and 2011 cowpea seasons, experiments were carried out to investigate the effect of intercropping between cowpea and each of Citronella grass and lemon grass on the populations of insect pests attacking cowpea . Intercropping in general, reduced the pests complex in cowpea fields. These reductions were 94.34 – 97.78, 75.98 – 80.19 and 50.64 – 58.37% in case of intercropping of Citronella grass with one, two and three rows of cowpea, respectively. The corresponding values in case of lemon grass were 97.92 – 99.11, 75.08 – 82.47 and 47.95 – 61.77%. Values of insect diversity index in 2010 season were 1.0725, 1.6583 and 1.6549 when citronella grass was intercropped with one, two and three rows of cowpea. The corresponding values of diversity index, in case of lemon grass were 0.8743, 1.0425 and 1.6053. Diversity index took almost the same trend in the second season (2011).