What attracts mosquitoes to me?

Mosquitoes find you by warmth, body odor, and the carbon dioxide (CO2) on your breath. Some people are more attractive to mosquitoes than others; this is mostly genetic.

Do mosquitoes serve a purpose in nature?

Yes. Many animals including dragon flies, hummingbirds, fish, water boatmen, and spiders feed on mosquito larvae or adult mosquitoes. However, there is no known species that feeds ONLY on mosquitoes. This means that controlling the mosquito population will not hurt these beneficial species. Some mosquito species, like Aedes aeygpti, are invasive – they don’t belong in our ecosystems at all, and can be completely eliminated from our county without ecological consequences.

What would happen if we eradicated mosquitoes?

Right now, it is not possible to completely eradicate all mosquitoes worldwide. Even if this did become possible, scientists are in agreement that we would not want to. Not only would it create an ecological disaster, but not all mosquito species transmit disease. Some don’t even bite!

Our goal in mosquito control is to reduce the population size of disease-transmitting mosquitoes enough that the threat to human health is minimized. This requires ongoing, year-round effort by the District.

How many kinds of mosquitoes are there?

There are about 3500 different species of mosquitoes world-wide, but only about 20 of those species are regularly found in San Mateo County.

Where do mosquitoes go during the day?

Some mosquito species are active during the day. Others rest during the day and feed at night. Mosquitoes like to rest in dark, humid areas, like in thick vegetation, under buildings, and inside sheds. Some species will even rest in dark, quiet areas indoors.

What do mosquito larvae look like?

Mosquito larvae look a little bit like very tiny tadpoles. You can see a video of them HERE (via Contra Costa County MVCD).

If you see something you think is a mosquito larva, you can bring a sample to the District office for identification.

Where do mosquitoes lay their eggs?

Mosquitoes lay their eggs on or very near to standing water.

Each species has a slightly different preference. Some like fresh water, others like brackish water. Some like clean water, others prefer dirty water. Some lay their eggs on the water’s surface, some on plants, and some lay eggs on damp soil at the waterline.

Do all mosquitoes bite?

No. Only female mosquitoes bite - they need the protein in blood to grow and lay eggs. Male and female mosquitoes both eat nectar and plant sugars in order to fly.

Some mosquito species don’t bite at all, while others prefer to feed on animals rather than humans. In fact, many mosquito species are specialized to a particular host. For example, the mosquito Uranotaenia sapphirina in Florida, strongly prefers to feed on worms.

How far can mosquitoes fly?

It depends on the species. Some kinds of mosquitoes, like the western encephalitis mosquito Culex tarsalis, can fly 10 miles. Other species, like invasive Aedes aegypti, never fly more than a few hundred feet from where they were born.

Do mosquitoes survive all year?

Yes. In San Mateo County, we have mosquitoes all year. However, different species are found during different seasons, and the overall number of mosquitoes is usually lower in the winter when the weather is cold. In snowy areas, adult mosquitoes survive cold weather (called overwintering) by seeking shelter and hibernating so they don’t have to eat or drink. When the temperature warms up, they wake up and fly out. Some species freeze to death as adults but survive the winter as larvae; diving down and either breathing through plant stems like a snorkel or looking for small pockets of air under the ice.

What are those giant mosquitoes I see sometimes?

Mosquitoes vary in size, but even the largest mosquito species found in San Mateo County are relatively small. The insects you see that look like giant mosquitoes are probably crane flies which are also called “mosquito-eaters”. Crane flies unfortunately do not eat mosquitoes – they feed on nectar.

What diseases can mosquitoes transmit?

Worldwide, mosquitoes transmit hundreds of diseases, such as West Nile virus, malaria, dengue, chikungunya, and Zika virus to name just a few. Fortunately, most of these diseases are not found in San Mateo County, however we detect West Nile virus in dead birds in San Mateo County nearly every year. 

If I get bitten by a mosquito, will I get sick?

Not necessarily. Just because you were bitten by a mosquito doesn’t mean the mosquito was carrying a disease that can make you sick. In fact, most mosquitoes are NOT carrying any diseases that you can get sick from. However, you should always take precautions, such as using EPA-registered repellents or staying indoors, when mosquitoes are biting. If you develop flu-like symptoms after a mosquito bite or see unusual swelling or rashes appear, see a healthcare provider.

Page last reviewed: September 20, 2023