What attracts mosquitoes

What attracts a mosquito to you

Only female mosquitoes bite, and they are looking for a blood meal to develop eggs. The search runs in stages, and each stage uses a different cue.

Carbon dioxide, at distance. This is the long-range signal, and it is why a trap that releases CO2 works at all while a UV lamp mostly does not. You exhale a plume; a host-seeking female flies up it. Anything that raises your output — exertion, talking, a larger body, pregnancy, a group of people — makes the plume stronger.

Body heat and moisture, close in. Within a few feet, warmth and humidity against the skin take over. A hot, sweaty person is a stronger target than a cool, dry one, which is the simplest explanation for why the person who just finished mowing gets bitten first.

Skin odor, which is mostly bacterial. The compounds mosquitoes respond to — lactic acid, ammonia and various carboxylic acids — come largely from the bacteria living on your skin rather than from sweat itself. Skin microbe populations differ a lot between people, and that difference is the best available explanation for why mosquitoes genuinely do prefer some people in the same yard.

Visual contrast and movement. At close range they use sight. Dark clothing against a lighter background reads as a target, and movement helps them close.

Alcohol and exercise, in the sense that both raise skin temperature and change what you give off. Neither is a large effect compared with CO2 and skin odor, but both are real.

What is not the explanation: blood type folklore, eating bananas, or taking vitamin B — the last of which has been tested as a repellent and does not work.

So of the things that draw mosquitoes to you personally, almost none are adjustable. You cannot stop exhaling. That is why bite prevention is about a barrier rather than about making yourself less interesting: an EPA-registered repellent on exposed skin, long sleeves in the evening, and lighter clothing. The CDC's bite-prevention guidance is a short page and worth reading once. Best yard mosquito repellents covers the products, and kid-safe mosquito repellents handles the age limits that come with each active ingredient.

What attracts mosquitoes to your yard

This is the useful half, because every item on this list is something you can remove.

Standing water, which is the whole game. Mosquitoes do not need a pond. The container species that bite in suburban yards will lay in anything that holds water for about a week — some will use a volume the size of a bottle cap. The mosquitoes biting you in your yard very largely bred in your yard or within a couple of hundred feet of it.

In rough order of how often they turn out to be the cause:

1. Plant pot saucers and the gap under a planter
2. Clogged gutters and downspout extensions
3. Buckets, watering cans, wheelbarrows, kids' toys and the base of a parasol
4. Tarps and furniture covers with a sag in them
5. Bird baths and pet water bowls left more than a few days
6. Corrugated drainpipe, which holds water in every corrugation
7. Old tires, the classic worst case
8. Trash and recycling bin lids, and any bin left open in the rain
9. Tree holes, rock hollows and the leaf axils of plants like bromeliads
10. Low spots in the lawn and blocked ditches that stay wet for a week

Damp shade to rest in. Adults spend the day resting in cool, humid, sheltered vegetation — dense ivy, overgrown shrubs against a wall, long grass at a fence line, the shaded side of a deck. A yard with a lot of that holds more biting adults than an open, mown yard even with the same amount of water.

Shelter from wind. Mosquitoes are weak fliers. Still, enclosed corners concentrate them, which is why the worst spot in a yard is usually a sheltered patio beside dense planting.

Your neighbors' water, which is the frustrating one. Flight ranges for common container species are short — a few hundred feet — so a neglected pool or a pile of containers next door really can be your problem.

What to change, in order of effect

1. Walk the property weekly and tip out every container. Set a day and do it. This is the single highest-value habit available to a homeowner and it costs nothing.
2. Treat water you cannot drain with BTI. A rain barrel, an ornamental pond with no fish, a blocked ditch, a wet low spot. BTI is a bacterial larvicide specific to mosquito and fly larvae, approved by the EPA and harmless to fish, pets and birds. Dunks for standing water, granules for fast knockdown and damp soil — mosquito dunks vs bits covers which goes where.
3. Clear the gutters and check downspout extensions. People miss these for years.
4. Cut back the resting habitat at the edges of the areas you use: thin dense ground cover, trim shrubs up off the soil, mow to the edges.
5. Protect the people for the evenings: repellent on exposed skin, long sleeves, and a fan on the patio. A box fan is an underrated tool — mosquitoes cannot hold a course in moving air.
6. Add devices only after the above. A cartridge repeller is the most effective device for a specific evening in a specific seat; a CO2-lure trap thins the population over weeks if you run it continuously at the edge of the yard. Neither substitutes for the water walk. Mosquito trap vs repellent sets out which to buy.

Things sold as answers to this question that are not

Bug zappers. They attract insects with ultraviolet light, which is not how a host-seeking mosquito navigates. The University of Florida extension write-up on the subject is titled "electric bug zappers are useless for controlling mosquitoes", and counts of what zappers catch find mosquitoes a tiny fraction of the total. Do bug zappers work has the detail.

Citronella candles and tiki torches. A weak, very local effect that collapses in any breeze. They are ambience with a marketing claim attached.

Ultrasonic repellers, including phone apps. No mechanism and no evidence, the same problem we document for rodent devices in do ultrasonic repellers work.

Plants that "repel" mosquitoes. Citronella grass, lavender and marigolds do not produce enough airborne compound to protect a yard. Crushing the leaves on your skin is a different thing from growing the plant.

Vitamin B patches and wristbands. Tested, ineffective.

Bats and purple martins. Both eat mosquitoes, and neither eats enough to change how many bite you. Mosquitoes are a small fraction of their diet.

The short version

You cannot make yourself uninteresting to a mosquito — the cues are carbon dioxide, heat, moisture and skin bacteria, none of which you control. What you can control is whether your yard produces thousands of them. Tip out the water once a week, treat what you cannot drain with BTI, cut back the damp shade at the edges of your seating, and put repellent on the people. That order is what actually works, and how to get rid of mosquitoes in your yard is the full version of it.