General information

Questions about Mosquito Biology

What attracts mosquitoes to me?

Mosquitoes find you by warmth, smell, 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 and no. Many other animals feed on mosquito larvae or adult mosquitoes. However, there is no known species that feeds ONLY on mosquitoes. Since mosquito predators also eat other insects, controlling the population of mosquitoes that transmit disease doesn’t significantly impact their food supply. Some mosquito species, like Aedes aeygpti, are invasive – they don’t belong in our ecosystems at all, and can be completely eliminated our county without ecological consequences.

What would happen if we eradicated mosquitoes?

Right now, it is not possible to completely eradicate all mosquitoes, or even a single species, worldwide. Even if this did become possible in the future, it’s unlikely that we would ever want to eradicate mosquitoes from the earth – not all species transmit disease, and some don’t even bite!

Instead, our goal is to reduce disease-transmitting mosquito populations 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 at https://youtu.be/L4Epg0MYGWw (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 near 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, while others lay eggs on damp soil at the waterline.

Do all mosquitoes bite?

No. Only female mosquitoes bite, never males. Some mosquito species don’t bite at all, while others prefer to feed on animals rather than humans.

What do male mosquitoes eat?

Male mosquitoes eat nectar and plant sugars.

How far can mosquitoes fly?

It depends on the species. Some kinds of mosquitoes can fly many miles in search of a meal. 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.

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.

What diseases can mosquitoes transmit?

Worldwide, mosquitoes transmit dozens of diseases that can make people sick. Fortunately, most of these diseases are very, very rare in our county. You can find more information about mosquito-borne disease here.

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 when mosquitoes are biting, and see a healthcare provider if you become ill.

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