In a field experiment , cowpea (variety Fetreyat) was sown dur­ing the 1998 autumn and the 1999 summer seasons . The highest per­centage of damaged pods was 86.26 % on November 10 (3^1° harvest time) and 77.50 % (2nd harvest time ) on June 29 . The highest per­centage of damaged seeds was 69.03% (^and harvest time )on October 27 and 79.62 % (rⁱ harvest time ) on July 12 . The highest number of caterpillars / pod was found during th 2^nd harvest time for the two plan­tations . There were correlations between damaged seeds and weather factors. In the laboratory the damage was estimated on four different types of cowpea seeds consumed by each larval instar to reach the prepupal stage . The 2^nd instar consumed 1.3 small and ripe seeds / larva until pupation .The highest percentage of pupation and moth emergence 84.99 and 91.66 was observed for the 5^th instar feeding on large and unripe seeds and the 3'^d instar on the same type of seeds. respectively . The longest period of nutrition was 12.66 days for the 3^rd instar until the prepupal stage .