Most mosquito species that bite people are crepuscular — active in the hour after sunset and the hour before sunrise. Understanding why explains which repellents work, where to sit, and why the same garden feels fine at noon and unbearable at eight.
How they find a host
Carbon dioxide first. A resting human exhales roughly 100–200 ml of CO2 per minute, and a female mosquito can detect a plume from 10–50 metres downwind. At close range she adds body heat, lactic acid from sweat, and visual contrast.
That hierarchy matters. A fan moving air disrupts the plume and is one of the few interventions that works on every species. It is also why a still, humid evening is worse than a breezy one.
Why dusk
Low light reduces evaporation and desiccation risk, and wind usually drops at dusk. The mosquito’s activity window is set by light level, not by clock time, which is why the last hour before a storm feels especially bad — falling pressure and still air.
Where they rest during the day
Shade, humidity and a vertical surface. The underside of leaves, the shaded side of a shed, under a deck, inside a garage, behind a downpipe. Residual sprays are applied to those resting surfaces, not to the open lawn; a mosquito that lands on a treated wall picks up a lethal dose before it ever reaches you.
What protects you
- EPA-registered repellent. DEET 20–30%, picaridin 20%, or IR3535. Apply to exposed skin, not clothing, and reapply per the label.
- Permethrin-treated clothing. Effective against mosquitoes and ticks. Never apply permethrin to skin, and keep treated clothing away from cats while wet.
- A fan. Moving air breaks the CO2 plume and slows flight.
- Long, loose clothing. Mosquitoes bite through thin, tight fabric.
What does not
Citronella candles reduce bites only in the immediate plume of smoke. Wristbands and garlic supplements have no consistent evidence. And a mosquito coil in an unventilated room is a respiratory risk, not a solution.
The yard layer
Reduce resting habitat: cut back ivy, thin dense shrubs, keep grass short near seating. Treat shaded walls and eaves with a residual insecticide late in the day, when the insects have settled. Combined with removing standing water, that is as close to a mosquito-free garden as a home programme gets.