The cotton aphid, Aphis gossypii Glover (Homoptera: Aphididae), is a polyphagous and cosmopolitan species. Under tropical conditions exhibit only parthenogenetic reproduction. It is the major pest on crops belonging to Cucurbitaceae and Malvaceae. Damage on crops is caused mainly by virus they transmit and includes yield loss and decreased fruit quality. Development of a biological control requires a better understanding of A. gossypii biology which is affected by environmental conditions specially temperature. The purpose of this study was to determine the life cycle of A. gossypii under laboratory conditions in order to use this information as a control for bioassays. Therefore a first instar aphid was transferred to a melon plant growing in a small pot that was isolated within a collapsible cage kept under controlled environmental conditions. Individuals in each observation system were observed every 24 hours. About six days later the reproduction period started and ended 14.6 days later. Sixty six nymphs were born during the life cycle with a mean of 3.5. Duration of the complete life cycle was 27 days.