Most mosquitoes here are a nuisance. This one is the reason to take the nuisance seriously. Aedes aegypti is the carrier of dengue, and it does not live in the swamp. It lives in the saucer under your potted plant.
Where you’ll see it
Around houses, because that is where it breeds: in small containers of clean standing water, of which every garden has a dozen. It bites in daylight, most in the hours after dawn and before dusk, and it prefers ankles.
What to know
Dengue circulates in Guanacaste every year, worst in the rainy season. Most infections mean a week of high fever, headache, pain behind the eyes and aching joints. A minority become severe, and a second infection with a different strain raises that risk. Fever plus those symptoms means a clinic, and no ibuprofen or aspirin until dengue is ruled out, because both can worsen bleeding.
The defence is unglamorous. Tip out standing water every week. Screen the windows. Sleep under a fan. Use repellent with DEET or picaridin in the mornings and evenings, particularly in the green season. It works, and it is how residents live here comfortably.
