(Summary) A daytime trap quite specific of adult Ae. aegypti mosquitoes has been designed and field-tested. The design is based on the attraction of contrasting gloss black and white panels, and involves a wind-orienting cover, a stationary cylinder housing the suction motor, and a cage to hold the trapped mosquitoes. A field test with genetically marked males has demonstrated its usefulness in estimating the proportions of the field population represented by the released Ae. aegypti mosquitoes.