A few species of mosquitoes rest in grassland during the day (field species) and are active in the same habitat at night. A number of other species rest in woodland during the day (woodland species) but at night fly out into grasslands. Collections from nocturnally-operated suction traps at distances of approximately 11 or 87 m from woodland showed equal numbers of field species at both distances whereas woodland species were taken in reduced numbers at 87 m. It is proposed that woodland species maintain visual contact with tall silhouettes such as the woodland edge.