MOSQUITO BIOLOGY for the HOMEOWNER

An extension program of the Department of Entomology, College of Agriculture 

& Life Sciences at Cornell University.

West Nile Virus

(print friendly 

version)

Mosquito Biology

(print friendly 

version)

Tick Biology

(print friendly 

version)

Insect Diagnostic 

Laboratory

Entomology 

Extension 

Programs

MOSQUITO BIOLOGY for the HOMEOWNER 

Renee R. Anderson and Laura C. Harrington

Table of Contents:

● Introduction

● Biology

❍ Eggs

❍ Larvae

❍ Pupae

❍ Adults

● Interesting Facts

● Management

❍ Larvae

■ Source reduction

■ Predators

■ Larvicides

❍ Adults

■ Physical exclusion

■ Adulticides

❍ Personal protection

■ Synthetic Repellents

■ Biopesticide Repellents

❍ Other Management Measures

● References

Introduction

Mosquitoes are flies in the family Culicidae. Over 3,000 known species of mosquitoes exist 

worldwide. More than 160 species have been documented in North America; at least 62 species occur 

in New York state.

Adult mosquitoes are characterized by having long, slender, needle-like mouthparts 

(proboscis), antennae, and legs. Their narrow wings are often covered with minute scales. Fine 

scales cover the mosquito body and vary in coloration from white, silver, or gold, to very dark. 

Pattern arrangement and scale coloration are often useful for identifying mosquito species.

Interesting Facts

● Adult female 

Toxorhychites

mosquitoes never take a blood meal. They are 

strict sugar-feeders. 

Toxorhychites

larvae consume the larvae of other species of 

mosquitoes. 

● Not all mosquito species will bite people or are 

able to transmit disease-causing agents. 

● Mosquitoes can ingest up to three times or 

more than their own body weight in blood. 

● Anopheles 

gambiae , the major mosquito 

vector of human malaria in Africa, is considered 

the world's "deadliest" animal. 

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Left: An adult female Culex restuans . 

Above: Close-up of a mosquito wing. 

Despite their delicate appearance, mosquitoes are aggravating pests of humans and other animals. 

Bites from mosquitoes can cause severe discomfort. The resulting intense itching is due to 

an immunological reaction to mosquito saliva injected into the bite wound.

The real danger, however, is that mosquitoes may vector disease organisms. Mosquitoes are capable 

of transmitting disease-causing viruses, protozoans, and filarial nematodes. The most 

important mosquito-borne diseases in the United States are caused by viral pathogens and include 

West Nile fever, eastern equine encephalomyelitis, St. Louis encephalitis, western 

equine encephalomyelitis, and La Crosse encephalitis.

Biology

Mosquitoes have four distinct developmental stages: egg, larva, pupa, and adult. Immature stages 

of mosquitoes require water to complete their life cycle. Mosquitoes are poikilothermic (coldblooded) animals, thus their rate of development and other aspects of their physiology are 

temperature-dependent. As the temperature increases, their development time shortens.

Eggs

 

Left: Clustering of Aedes 

aegypti eggs. The scale is in 

millimeters. 

 

Right: An egg raft of Culex p. 

pipiens . The scale is in millimeters. 

A freshly laid egg is light in color and darkens within a few hours. Mosquito eggs are oval and 

about 1/40th of an inch (0.635mm) long. Eggs are either deposited singly or as an egg raft depending 

on the type of mosquito. A standard egg raft is about 1/4 inch (6.35mm) long and contains 100-

200 eggs. Some species of mosquitoes lay their eggs singly and deposit them directly on water 

or floating aquatic vegetation. Others will lay their eggs on moist soil that is subject to periodic 

flooding, or above the water line in natural and artificial containers. The number of single eggs laid 

per batch varies within and between mosquito species and can range from 60 to 200.

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Left: Clustering of Oc. j. 

japonicus eggs on the inside rim of a plant 

pot. 

Larvae

Larvae will emerge from eggs within 2-3 days when environmental conditions are ideal. All 

mosquito larvae go through four developmental stages called instars. First instars are barely 

noticeable to the human eye. Last larval instars of some species can be approximately 1/2 

inch (12.7mm) long. Larvae move through the water in a serpentine motion. When they sense a 

shadow or movement in their habitat, larvae will quickly dive to the bottom to avoid the source 

of disturbance.

 

One first (upper right) and two fourth instar larvae of Oc. 

j. japonicus . The scale to the left side is 

in millimeters. 

Larvae have a well-formed head and lack legs. Upon careful inspection one can distinguish the 

wider thorax from the long and slender abdomen. A tube-like structure, called a siphon, is located at 

the tip of the abdomen. Larvae use the siphon to breathe air from the water surface. Larvae 

possessing a siphon (Culicine) hold their body roughly at a 45-degree angle from the surface. Species 

of mosquitoes lacking a respiratory siphon (Anopheline) hold their body horizontal to the water 

surface. They obtain air through openings located on the dorsal surface of the abdomen. A few 

species will bore their siphon into stems of aquatic plants to obtain oxygen.

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Anopheles punctipennis

larva; note the absence of a siphon. The scale to the left side is in millimeters. 

Mosquito larvae can be found in a wide variety of habitats, including temporary floodwater and 

snowmelt pools; more permanent water habitats like marshes, swamps, lagoons, and ponds; 

stagnant waters; and natural and artificial containers. Shallow water is ideal for larval survival 

because there is less turbulance and wave action. Upper water movement interferes with the 

surface feeding of some mosquito species, and in most species, it hinders the larvae and pupae 

from obtaining oxygen at the air-water interface. A deep-water environment prevents bottomfeeding water from reaching food that has accumulated at the lower levels of the water column. 

Water quality in larval habitats can vary from fresh to saline to high in organic wastes. Different 

species can tolerate and thrive in water with varying degrees of organic content.

Mosquito larvae eat a variety of dead and living organisms, including detritus, algae, bacteria, and 

fungi. Some mosquito species are predaceous and feed on other mosquito larvae and 

small invertebrates. Depending on water temperature, crowding, and food availability, the larval stage 

is typically completed in 5-6 days.5,7

Pupae

Mosquito pupae are active when compared to other insect pupae. Pupae move in a somersault 

fashion through the water. Pupae breathe through tubes located on the thorax and will remain at 

the water surface unless they are disturbed. This non-feeding stage can be completed in as few as 2-

3 days.5,7

 

A mosquito pupa. The scale to the left side is in 

millimeters. 

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Adults

Both male and female mosquitoes feed on sugar sources such as plant nectar and honey dew, but 

only females feed on blood. Female mosquitoes use proteins and lipids from the blood meal to develop 

a batch of eggs. There are a few exceptions to this rule. Some species are autogenous, meaning 

a female is able to utilize energy reserves from the larval stage to produce eggs without a blood meal.

 

Female 

Ochlerotatus 

j. japonicus blood 

feeding. 

Many species of mosquitoes are specific in their host preference for birds, mammals, or coldblooded vertebrates such as reptiles and frogs. Consequently, various mosquito species use a 

wide variety of cues to find a suitable host, often involving a variety of complex interactions. 

This complex of cues is still not fully understood by scientists. These cues can be either odors 

emanating from skin or breath, or visual cues such as movement or contrast of a potential host with 

the surrounding background. Carbon dioxide is a major cue and is often used as bait in mosquito traps.

Several hundred compounds found in human breath, secretions, and sweat glands have been 

identified and vary in their degree of attractiveness to female mosquitoes.6 Some of the more 

attractive odors include: carbon dioxide, alanine, lysine, lactic acid, and estrogen. Some 

chemicals emanating from a potential host may be more important for certain species of mosquitoes. 

In other mosquito species, these very same odors may play a secondary role, no role, or act to 

repel mosquitoes.6

The distance that mosquitoes can fly is difficult to generalize because mosquito species vary in 

their flight range. Some species can fly long distances (up to 10 km), but most do not travel more 

than several yards.6,7,15

Management

New York state has specific environmental laws, rules, regulations, and policies relating to 

mosquito control and management. Area-wide control of adult mosquitoes and control of 

mosquito larvae and pupae in wetlands, waterways, catch basins, and public areas fall under 

these regulations and cannot be performed by the general public. Integrated Pest Management 

(IPM) uses a strategic approach to controlling mosquitoes. IPM is most likely to be effective when 

several techniques are used together. The following mosquito IPM recommendations are applicable 

to homeowners and include measures you can take only with your own property.

Larvae

Source reduction

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An effective, long-term method of minimizing mosquito problems is reducing or eliminating 

potential breeding sites around the home. Water is necessary for mosquito development. Containers 

of all types can hold water and potentially serve as larval habitat for certain peridomestic 

species. Properly dispose of old tires, cans, bottles, water-collecting rubbish, and other unused 

or unwanted containers. Eliminate standing pools of water created from tire ruts or similar sites that 

hold water for more than one week. Avoid excess watering of lawns and gardens. Control seepage 

from air-conditioning units and ill-fitting garden hoses.

 

Water holding tire ruts are another example of mosquito larval 

habitat. 

 

Oc. J. Japonicus eggs on the rim of a flower 

pot. 

Periodically clean birdbaths, pet dishes, plant pots, rain barrels, and kiddie pools and monitor them 

for mosquito production. Keep an eye out for small black mosquito eggs pasted around the rim of 

these containers or black egg rafts floating on water. When cleaning containers, be sure to 

thoroughly scrub the sides in order to dislodge any attached eggs. Survey your yard for mosquito 

larvae in other types of water-holding containers such as tree holes, ornamental ponds, and clogged 

rain gutters.

 

Tree holes provide excellent habitat for certain species of 

mosquitoes. 

 

A clogged rain gutter on a 

house. 

Predators

Mosquito larvae confined to containers, ornamental ponds, or small temporary pools may be controlled 

in certain situations by biological predators (although the efficacy of this approach has not been 

fully investigated by scientists). Larvae-eating fish, immature dragonflies and damselflies, 

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aquatic beetles, cannibal mosquito larvae, and certain aquatic planaria, type of flatworm, will feed 

on mosquito larvae and may help reduce larvae in breeding sites if initial larval numbers are not 

high. Consider encouraging the establishment or conservation of these predators. Distributors of some 

of these predators may be found on the Internet. Stocking of mosquito-eating fish requires a 

special permit from the New York State Department of Environmental Conservation.

Larvicides

Larvicides are products that kill mosquito larvae. Targeting larvae is more desirable than 

controlling adults because the larvae are concentrated in a relatively small area. Products 

containing Bacillus thuringiensis

variety israelensis (Bti, a microbial compound) and methoprene (an 

insect growth regulator) are currently available over-the-counter for homeowner use in New York 

state. Advantages of these compounds are their specific action against insects and minimal impact 

on nontarget organisms such as fish and other aquatic animals.

The microbial insecticide, 

Bacillus thuringiensis

variety israelensis , needs to be consumed by mosquito larvae and must 

be applied well before the last larval instar (stage). Its effectiveness depends upon the mosquito 

species present, water quality, and size of the initial larval population. The product is made from 

a dormant spore of a soil-inhabiting bacterium. Ingestion of the spore disrupts the gut wall of 

larvae, causing death. According to the Environmental Protection 

Agency, Bacillus thuringiensis

variety israelensis does not pose risks to wildlife, non-target species, or 

the environment.18

Mosquito larvae in water treated with the insect growth regulator methoprene continue to feed and 

grow normally until the pupal stage. Exposure of larvae to methoprene disrupts normal molting into 

the pupa and results in death. The Environmental Protection Agency states that methoprene toxicity 

to fish and birds is low, and methoprene is nontoxic to honeybees.18

Adults

Physical exclusion

An often overlooked but highly effective means of controlling mosquitoes is the use of tight-fitting 

and well-maintained window and door screens with a 16-inch mesh. Make sure there are no holes 

in screens, because mosquitoes can easily find these and enter your home. Also make sure there are 

no gaps between the screen and window frame. Be sure to calk and seal all cracks around 

windows. Some mosquito species are attracted to outdoor lights. Reduce unnecessary lighting, or 

move the lights away from sensitive areas such as doorways. Replace outdoor lights with yellow 

bug lights. Bug lights are less attractive to many kinds of insects and can be found wherever 

household light bulbs are sold.

 

Torn window screens can easily allow mosquitoes to enter your home. 

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Adulticides

Adulticides are substances that kill adult mosquitoes. Yard foggers or sprays are available 

to homeowners for temporary control of adults in the yard. These products contain various 

formulations of chemical insecticides such as pyrethrin, malathion, or permethrin. These products 

may only result in temporary control of mosquitoes and should only be considered as a last resort. 

The duration of their activity depends on the method of application and environmental conditions such 

as rain, sunlight, and high temperature. Furthermore, they are much more toxic to humans, pets, 

and other animals than the larvicidal compounds. Read and follow directions on the label; remember, 

it is the law when applying pesticides.

Personal protection

You can take individual measures to minimize your exposure to mosquito bites. If possible, modify 

your routine or other outdoor activities to minimize your time outdoors during peak mosquito 

activity. Predicting "peak mosquito activity" is difficult because it varies locally and seasonally, and 

it depends on the mosquito species present in your area. Many species are active during early 

evening hours. Some mosquitoes are active during night, while others will readily bite during 

daylight hours. There also seems to be a difference in individual human attraction to mosquitoes. Be 

sure to pay attention to the biting pressure your children may receive while they are outside 

playing. Wear protective clothing such as long sleeve shirts, long pants, socks and shoes. Consider 

using an insect repellent while outdoors to reduce your chances of being bitten. If you use a 

repellent, make sure you read and understand the label prior to each use. Some repellent 

formulations can be applied only to skin, on both skin and clothing, or only on clothing! Insect 

repellents come in a variety of formulations: aerosol sprays, pump sprays, lotions, liquids, and 

with sunscreen. Common ingredients found in over-the-counter repellents belong to two 

broad categories: synthetic chemicals and biopesticides.

Synthetic Repellents

Two common synthetic repellents have DEET (N,N-Diethylm-toluamide ) or permethrin as active ingredients. DEET can be 

applied directly to the skin or clothing. However, DEET can damage some types of fabrics, watch 

faces, and painted and varnished surfaces. DEET cannot be applied to skin that is covered with 

clothing. The United States Environmental Protection Agency (EPA) has completed an 

extensive reevaluation of DEET and has "concluded 

that as long as 

consumers follow 

label directions and 

take proper 

precautions, 

insect 

repellents containing 

DEET do not present 

a health concern ."19 Overall, studies have shown 

that higher concentrations of DEET are correlated with a greater length of protection but 

products containing lower concentrations of DEET in the 15-25% range afford good protection.2,3,8,9

The length of protection provided will depend on various conditions such as how much you 

sweat, environmental temperature, and mosquito species present. Starved mosquitoes are not as 

easily deterred by DEET.20 Do not overuse products containing DEET, and be sure to wash treated 

skin with soap and water upon returning indoors. The American Academy of Pediatrics (AAP),1

the Environmental Protection Agency (EPA),17 and the National Pesticide Information Center (NPIC)

14 provide additional information on DEET. The Internet address for these organizations can be found 

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in the reference section. Persons concerned with using DEET-based products on their children 

should contact their health care provider.

Permethrin (0.5% active ingredient) cannot be applied directly to the skin. It is applied to clothing 

and dried before the clothes are worn. The advantage of permethrin is that it is a toxicant and will 

kill any mosquitoes landing on treated clothing.

Biopesticide Repellents

There are non-DEET and non-permethrin repellents labeled for use against mosquitoes; however 

most biopesticide repellents do not provide the same degree of complete protection as 

synthetic repellents.2,3 A laboratory based study found that protection afforded by a soybean oil 

repellent (2% active ingredient) was not significally different from the complete protection time of 

a product with a low concentration of DEET (4.75% active ingredient).9 The range of 

complete protection for the 2% soybean repllent was 16-195 minutes while the 4.75% DEET 

product provided 45-120 minutes of protection. Active ingredients of other biopesticide 

repellent products include: oil of citronella, oil of eucalyptus (p-menthane-3, diol), and IR3535 (found 

in products sold through catalog cosmetic distributors).

Other Management Measures

Contrary to popular belief, bug zappers do very little in controlling adult mosquitoes. Studies have 

shown that far more beneficial insects are killed by bug zappers than are pest species.10 There 

is evidence from at least one backyard study that electric bug zappers increased the number of 

female mosquitoes present in the yards as opposed to yards without the devices, and were not 

effective in reducing the number of female mosquitoes landing on people.13,16 Similar results were 

found with electronic mosquito repellers. Persons using the devices recovered more female 

mosquitoes landing on them when compared to those not using them.11 The repellers did not afford 

any protection against bites.11

Scientific studies to date have demonstrated that propane-powered mosquito traps do collect 

adult mosquitoes.4,12 However, no studies exist that document the efficacy of these types of traps 

in significantly reducing mosquito populations to the level that they prevent bites, or decrease the risk 

of contracting a mosquito-borne disease.

Please contact your local Cornell Cooperative Extension office for current chemical 

control recommendations for mosquito larvae and adults. Remember, the label is the law.

Contact the New York state Department of Environmental Conservation for any regulations that 

may apply to your particular situation.

References

1. American Academy of Pediatrics. Accessed on March 12, 2004, at http://www.aap.org/. 

2. Anonymous. 1993. Bug off! How to repel biting insects. Consumer Reports. July: 58(7): 451-454.

3. Anonymous. 2000. Buzz off! Consumer Reports. June. 65(6): 14-17.

4. Burkett, D. A., W. J. Lee, K. W. Lee, H. C. Kim, H. I. Lee, J. S. Lee, E. H. Shin, R. A. Wirtz, H. W. Cho, D. 

M. Claborn, R. E. Coleman, and T. A. Klein. 2001. Light, carbon dioxide, and octenol-baited 

mosquito trap and host-seeking activity evaluations for mosquitoes in a malarious area of the republic 

of Korea. Journal of the American Mosquito Control Association. 17(3): 196-205.

5. Clements, A. N. 1992. The biology of mosquitoes. Vol. 1. Development, nutrition and 

reproduction. Chapman and Hall, New York.

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6. Clements, A. N. 1999. The biology of mosquitoes. Vol. 2. Sensory reception and behaviour. CABI 

Publishing, New York.

7. Foster, W. A. and E. D. Walker. 2002. Mosquitoes (Culicidae). In: Mullen, G. and L. Durden (Eds.) 

Medical and 

veterinary entomology . Academic Press, 

New York.

8. Fradin, M. S. 1998. Mosquitoes and mosquito repellents: a clinician's guide. Annals of Internal Medicine. 

128(1): 931-940.

9. Fradin, M. S. and J. F. Day. 2002. Comparative efficacy of insect repellents against mosquito bites. 

New England Journal of Medicine. 347(1): 13-18.

10. Frick, T. B. and D. W. Tallamy. 1996. Density and diversity of nontarget insects killed by 

suburban electric insect traps. Entomological News. 107(2): 77-82.

11. Helson, B. V. and R. E. Wright. 1977. Field evaluation of electronic mosquito-repellers in Ontario. 

Proceedings of the Entomological Society of Ontario. 108: 59-61.

12. Kline, D. L. 2002. Evaluation of various models of propane-powered mosquito traps. Journal of 

Vector Ecology. 27(1): 1-7.

13. Nasci, R. S., C. W. Harris, and C. K. Porter. 1983. Failure of an insect electrocuting device to reduce 

mosquito biting. Mosquito News. 43(2): 180-184.

14. National Pesticide Information Center. Telephone number 1-800-858-7378. Accessed March 12, 2004 

at http://npic.orst.edu/. 

15. Service, M. W. 1997. Mosquito (Diptera: Culicidae) dispersal -- the long and short of it. Journal of Medical 

Entomology. 34(6): 579-588.

16. Surgeoner, G. A. and B. V. Helson. 1977. A field evaluation of electrocutors for mosquito control 

in southern Ontario. Proceedings of the Entomological Society of Ontario. 108: 53-57.

17. United States Environmental Protection Agency. Accessed March 12, 2004, at http://www.epa.gov/. 

18. United States Environmental Protection Agency. Larvicides for mosquito control. EPA Publication 735-

F-02-007. Accessed March 12, 2004, at http://www.epa.gov/pesticides/factsheets/larvicides4mosquitos.

htm. 

19. United States Environmental Protection Agency. Re-registration of the insect repellent DEET. 

Accessed March 12, 2004, at http://www.epa.gov/pesticides/factsheets/chemicals/deet.htm. 

20. Xue, R. D. and D. R. Barnard. 1999. Effects of partial blood engorgement and pretest 

carbohydrate availability on the repellency of deet to Aedes 

albopictus . Journal of Vector Ecology. 24(2): 111-114.

This publication contains pesticide recommendations. Changes in pesticide regulations occur 

constantly and human errors are still possible. Some materials mentioned may no longer be available 

and some uses may no longer be legal. All pesticides distributed, sold or applied in New York State 

must be registered with the New York State Department of Environmental Conservation (DEC). 

Questions concerning the legality and/or registration status for pesticide use in New York State should 

be directed to the appropriate Cornell Cooperative Extension Specialist or your regional DEC 

office. READ THE LABEL BEFORE APPLYING ANY PESTICIDE.

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