The biology of a mosquito
Curious about the mosquito life cycle? Read below to learn about a mosquito’s stages of life, how they lay eggs, find meals and much more.
- Mosquitoes are insects which belong to the fly family (diptera).
- Only female mosquitoes take blood meals, needed for egg laying, and can live for months. Males typically live for about a week and do not take blood meals.
- Mosquitoes hatch from eggs laid in places which hold or will fill with water.
- Larvae, also known as “wrigglers,” will hatch and lie below the water surface, feeding on microscopic organisms such as bacteria.
- In under a week, larvae develop into pupae, also known as “tumblers.” Pupae do not feed and usually will turn into adult mosquitoes within three days.
- Various clues enable mosquitoes to find blood meals in people and animals.
- Mosquitoes can detect carbon dioxide exhaled by hosts.
- They can sense body chemicals, such as lactic acid in perspiration
- Some people are just more attractive to mosquitoes than others
- Once a mosquito finds a host it will use its needles to probe beneath the skin to find blood vessels. View the video below from PBS on How Mosquitoes Use Six Needles to Suck Your Blood
How Mosquitoes Use Six Needles to Suck Your Blood – PBS
You can find a transcript of this video here.
If you are interested in learning more about mosquito biology, the CDC provides a further breakdown of the parts of an adult mosquito. The information above has been summarized from the Illinois Department of Public Health’s Prevention & Control article Mosquitoes and Disease.
Common Illinois Mosquitoes
The most common mosquitoes in the district are the Aedes and Culex species. Open the dropdowns below to learn more about each type.
- Also known as nuisance or floodwater mosquitoes.
- Can come out in huge numbers 5-10 days after a big rain event.
- Like to take blood meals from mammals – including humans.
- These are the mosquitoes most encountered in yards and forests.
- Not a serious threat of spreading human diseases in our area.
- Prefer cool, wet weather – generally we see these mosquitoes in spring and early summer.
- Lay eggs in moist soil and only hatch when covered with water – the eggs can last for 2 to 5 years and still emerge when covered in water.
Life cycle of an Aedes mosquito
- Lay eggs directly in stagnant, organically enriched water (ditches, stormwater catch basins, water holding containers in yards).
- Prefer hot and dry conditions
- Prefer to feed on birds but will feed on people if given the opportunity.
- More common in urban/suburban areas
- More common in mid to late summer.
- Carry diseases like West Nile Virus
Life cycle of a Culex mosquito
Invasive species spreading in the District: The Asian Tiger mosquito
About Aedes albopictus, AKA “Asian Tiger Mosquito”
The Asian Tiger mosquito is a unlike other mosquitoes as it is a daytime feeder, most active during early morning and late afternoon. They are recognizable by their distinctive jet black body accented by bright white scales and “racing stripe” down the center of it’s back. The Asian Tiger mosquito flies close to the ground, typically biting ankles, legs and elbows. They are “container breeders,” needing as little as a teaspoon of water, which makes artificial containers holding water a popular breeding ground.
It was first brought to the United States in tire casing in 1985 and has steadily been spreading since. View the GIFs of yearly population data below to see the increase in the Asian Tiger mosquito in Cook County and the NWMAD District.
Asian Tiger Mosquito Fast Facts
Identifying the “Tiger”
Coloration:
Distinctive jet-black body accented by bright white scales.
The “Racing stripe”:
A single, bold white longitudinal stripe down the center of its back – the most reliable identifying mark.
Size:
Generally smaller than native Culex or Aedes species, but notably more aggressive
Biting behavior
Unlike most mosquitoes active at dusk or night, the Asian Tiger is a daytime feeder – most active during the early morning and late afternoon.
Stealthy and Low:
Flies close to the ground, typically biting ankles, legs and elbows.
“Nervous” Feeders:
Easily startled – they dart away, then return to bite multiple times to finish a single meal.
Opportunistic Hosts:
Prefer humans, but will also feed on mammals, birds, and reptiles.
Where they breed
The Asian tiger is a “container breeder” – it needs no swamp or pond. As little as a teaspoon of water is enough.
Artificial Sources:
Clogged gutters, discarded tires, birdbaths, flowerpot saucers, corrugated plastic downspout extensions.
Natural Sources:
Tree holes, bamboo stumps, and plants like bromeliads
Resilient Eggs:
Desiccation-resistant – eggs survive months in dry container and hatch when flooded by rain or irrigation.
Why they stay close to home
Limited Flight Range:
Asian tiger mosquitoes rarely fly more than 200 meters from where they were born. They find everything they need right in our yards.
It is vital to check every water-holding site on your property because they are “skip-ovipositors.” A single female Asian tiger mosquito spreads her eggs across multiple containers.
Take Action: “Tip ‘n Toss” weekly
Check every possible water-holding site on your property and empty it. Do this every week to break the breeding cycle.
- Inspect: Walk your property and identify all containers that can hold water
- Tip & Toss: Empty standing water from gutters, pots, tires, saucers, and more.
- Repeat Weekly: Consistent action is key – eggs hatch as soon as containers are flooded
Find more resources on emptying backyard water sources, repellents and other protective tactics on the Fight the Bite page.
Tiger mosquito spread in Cook County
The GIF below showcases the spread of the Asian Tiger mosquito in Cook County since 1987.
Tiger mosquito spread in the NWMAD District
The GIF below showcases the spread of the Asian Tiger mosquito in the NWMAD District since 2022.
West Nile Virus
West Nile Virus (WNV) is a type of viral encephalitis disease which causes swelling of the brain. WNV came to the United States in 1999 via an infected mosquito or bird and was first detected in Illinois in 2001, with a major outbreak in human cases the following year.
Birds act as reservoirs for this disease, housing it without themselves being seriously affected. When a mosquito bites an infected bird, it can become a vector – an organism which transmits the disease to other animals. When the infected mosquito bites a human, it transmits the disease. If you see a dead bird with no obvious cause of death other than disease, please submit a report to the Cook County Department of Health. Only report dead birds June 1 through September 30.
Most human infections with West Nile virus occur in late July through September.
Fun Fact!
“Horses and humans are generally thought of as ‘dead-end’ hosts because they do not produce enough virus to infect mosquitoes. Thus, dead-end hosts are not involved in the spread of disease.”
How West Nile Virus affects humans
- Only 1 in 5 people infected with West Nile virus will become ill.
- Common symptoms are fever, headache, joint pain, rash and nausea. Usually, symptoms resolve within a week.
- ~ 1% of people infected will develop encephalitis – swelling of the brain. 10% of these people will die.
- Groups most likely to become seriously ill are people over the age of 65 and people with a weakened immune system.
Protect yourself from West Nile Virus
- Avoid going outdoors during dawn and dusk, as Culex mosquitoes are most active during these times.
- Wear insect repellent, long sleeves and pants. The EPA provides further information on using repellent to protect against mosquito borne illnesses.
- Empty containers of standing water on your property
- Fill out a Service Request for any standing water on your property which you cannot empty.
- View our Fight the Bite page for more detailed information on how to protect yourself and loved ones.
- Check the Cook County Department of Public Health’s Weekly West Nile Virus Surveillance Data.
- Check the Personal Protection Index on the NWMAD homepage and Fight the Bite page.
A note from NWMAD’s Entomologist, Patrick Irwin, PhD
During summers with high temperatures and drought-like conditions we see the most human cases of West Nile virus. When there seem to be fewer biting mosquitoes that is the time to take the most precautions against West Nile virus.
Testing for adult mosquitoes
Patrick Irwin, PhD is the Entomologist at Northwest Mosquito Abatement District. From late April till early October, the NWMAD Lab team performs mosquito surveillance by collecting mosquitoes, Monday through Friday, caught in one of 35 possible traps set throughout the district.
NWMAD’s Lab team uses two types of traps. New Jersey traps are used to catch and track nuisance mosquitoes. Gravid traps catch and track disease vector mosquitoes. Back in the lab, the team count and identify the species and gender of mosquitoes in the traps. Female Culex mosquitoes caught in the Gravid traps are tested for West Nile virus. Having traps throughout the northwest suburbs of Cook County allows the Lab team to calculate the risk of West Nile virus for each township in the district.
Lab assistant checking Gravid trap.
Lab assistant checking New Jersey trap.
Integrated Mosquito Management Practices
NWMAD’s Integrated Mosquito Management Practices include water management, larval surveillance, abatement, adult surveillance, and adulticiding. Explore these practices more in depth on the Operation Overview page.
The main forms of treatment NWMAD implements is larvicide (control of mosquitoes in the larvae stage) and adulticide (control of mosquitoes in the adult stage). The Treatment Programs page further explains these forms for mosquito control.