Advances in methods for colour marking of mosquitoes

BACKGROUND: Different techniques are available for colour marking insects and each technique may be suitable for different insect species. Mosquitoes can be marked to determine population size, distribution and flight distance or distinguish closely related species. In this study, two methods of colour marking mosquitoes were described in detail and the impact of both methods on the survival and host-seeking behaviour of the malaria mosquito Anopheles gambiae sensu stricto was investigated. METHODS: Mosquitoes were marked in groups with fluorescent powder or fluorescent dye. The powder was applied by creating a cloud of powder in a paper cup and the dye was applied with an airbrush. The effect of marking on the survival of mosquitoes of different age groups was tested under controlled conditions. The effect of marking on the host seeking response of the mosquitoes was tested in an olfactometer with human and cow odour as baits. RESULTS: No effect of either of the marking methods was found on the survival of mosquitoes that were treated 1 or 3 days after emergence, however, the survival of mosquitoes treated 5 or 9 days after emergence was significantly reduced. The host-seeking response of mosquitoes to human or cow odour was tested in a dual-port olfactometer and was not found to be affected by treatment with fluorescent powder or dye. CONCLUSIONS: Both methods are suitable for colour marking large groups of mosquitoes. Marking with fluorescent powder, however, is preferred because the method is simpler, visible without a UV light and no specific materials are required.