There are hundreds of different species of mosquitoes--so many that even scientists don't agree on how they should be classified. Researchers have spent thousands of hours exploring, catching and staring at mosquitoes under magnifying glasses and microscopes, grouping them into genera (the plural of genus) and species.
Can you imagine paying this much just for one professor's book about mosquitoes? Amazing. But people who dedicate their lives to learning about these little insects are actually doing important work, because each kind of mosquito has a slightly different secret for surviving cold, drought, predators and other dangers, and different types of mosquitoes carry different diseases. By classifying them into species and studying their habits, scientists can figure out the best way to get rid of the ones that carry the worst diseases.
Listed below are the major genera of mosquitoes found in the United States and some of the important species within each genus. For illustrations of the main differences between the eggs, larvae, pupae and adults of three common genera, Anopheles, Aedes and Culex, see this pdf chart.
There's at least one species of the Anopheles genus in every state of the U.S. except Hawaii. They're the easiest genus to recognize because they rest with their body slanted, unlike other genera who keep their body level. They used to carry malaria in the United States, though they rarely do now, but they still spread the disease in other countries.
The adult females lay their eggs individually in pools of water, with little floats attached to keep the eggs on the surface until they hatch. They can lay over a hundred eggs after each breeding. After a few days, the eggs hatch, producing larvae which become adults in a week or several weeks. The larvae rest parallel to the water surface, rather than hanging down from it like most mosquito larvae.
Anopheles mosquitoes usually bite at night, just after dusk and just before dawn. Fertilized females spend the winter hibernating.
Anopheles quadrimaculatus, the malaria mosquito, enters houses and is the mosquito of this genus most apt to bite people. It lives throughout the eastern and central U.S. and lays its eggs in the shallow, clear water of swamps and ponds which are not too stagnant or acid. They bite at night, choosing livestock as well as people. In winter, the fertilized females hibernate in protected areas, coming out on warm days.
Anopheles walkeri lives in places similar to quadrimaculatus, though it overwinters in egg form, producing a special "winter egg" to survive the cold.
Anopheles freeborni lives in the western half of the United States, and bites aggressively at twilight and dawn, choosing both humans and animals and entering houses or barns. It can spread malaria and used to be a significant vector of that disease in the west. Its larvae develop in the standing water of irrigation canals, stream edges and rice fields. The adults hibernate, coming out on warm days, then beginning to breed in early spring.
About half of the mosquitoes in North America are in the Aedes genus. They thrive in cooler temperatures, not requiring tropical climates. Their eggs can withstand long periods of being dry or cold, so in cold climates, the adults die off while the eggs survive until spring. They lay eggs individually at or above the waterline or on dry ground. The eggs wait until wet weather or flooding dampens them, before they hatch. The larvae live in puddles, pools, marshes or wherever there's temporary standing water. The adults usually bite in the evening, though some species bite in the day or night. Aedes mosquitoes carry diseases, and can be vicious biters, found in large numbers.
Aedes aegypti was infamous for spreading yellow fever. Originally from Africa, it's now found throughout most of the southeast U.S. and the larvae will thrive in any stagnant water around cities or homes, from old tires to gutters. Sensitive to cold, it overwinters by leaving eggs to hatch when warm weather returns, but can go from egg to adult in 10 days when temperatures are hot. It prefers to bite in the morning or late afternoon rather than at night and will choose people over animals.
Aedes albopictus, the Asian tiger mosquito, arrived in the U.S. as eggs or larvae in cargo and now is established throughout the east and midwest. It is a possible vector for dengue, dog heartworm and encephalitis, and can breed in small water containers like Aedes aegypti, which it is out-competing in some areas.
Aedes canadensis is common in the northern U.S., though it breeds in woodland habitats and stays close there, rather than venturing to cities. In the spring, it appears early in the year, at the first sign of warm weather in March. It can carry equine encephalitis and dog heartworm.
Aedes sollicitans breeds in salt marshes along the mid and north Atlantic coast. The adults can swarm and migrate in the evenings, congregating in towns 10 miles or more from the marshes, where they bite aggressively at night and even in the day if stirred up from their hiding places. They carry Eastern equine encephalitis to horses and people.
Aedes nigromaculis breeds in floodwaters and irrigated areas of the western plains, as far south as Mexico, and California. It bites aggressively and painfully, and can spread encephalitis.
Culex mosquitoes prefer the tropics, but there are about a dozen species somewhat common in the United States. They lay their eggs connected together in groups called "rafts," which float on quiet pools of water as big as lakes or as small as buckets, or as stinky as sewage cesspools. One raft may contain a hundred or more eggs, which hatch in two or three days. The adults usually bite in the evening or at night and have been blamed on disease outbreaks in several places.
Culex erraticus is a small, dark species of the southeastern U.S. The larvae live in ponds and are also found in Arkansas rice fields. The adults bite hard, but prefer birds to people.
Culex nigripalpus prefers the warm temperatures of Florida and has been linked to outbreaks of St. Louis encephalitis there.
Culex stigmatosoma is common in California and the Pacific coast in general, but prefers biting animals to humans.
Culex pipiens, also called Culex fatigans, the house mosquito, is divided into several subspecies, but at least one kind is found in every state. The adults don't fly far, but their larvae thrive in any stagnant water, so they're common around houses wherever water is allowed to accumulate in puddles, old tires, barrels or gutters. They can carry St. Louis encephalitis.
Culex salinarius doesn't mind salt water, so it lives near the Atlantic and Gulf coasts, biting at night. The larvae live in either fresh or salt marshes, roadside ditches or cattail bogs.
Culex tarsalis spreads encephalitis to people and horses west of the Mississippi, and occasionally is found in the east too. The larvae can live in irrigation puddles, ditches, ponds, drinking troughs or open cesspools. The adults bite at night, preferring birds but also biting livestock and humans. They hide in sheltered areas during the day and, like most Culex mosquitoes, survive the winter by hibernating.
There are eight species of the Culiseta genus in the United States. They are unusual in that they don't mind cold weather. In the south, some will come out of hibernation in the middle of winter if there are a few warm days. The adults usually prefer to bite animals rather than people and they have been blamed for outbreaks of equine encephalitis.
Culiseta incidens has spotted wings. It's generally found from Texas west and prefers biting livestock rather than people.
Culiseta inornata lives everywhere in the United States outside of northern New England. It prefers biting animals to people and doesn't mind cold weather, sometimes coming out of hibernation in the winter while snow is still on the ground, earning the nickname "snow mosquito."
Culiseta melanura lives throughout the eastern United States. Scientists believe it's the main vector for spreading Eastern equine encephalitis between birds, but it rarely bites humans.
The Mansonia genus has only one species of importance in the United States, since it prefers tropical weather.
Mansonia titillans lay their eggs on the underside of water lettuce leaves in Florida. The larvae live among the roots of the plant and grow slowly, emerging the next year as adults that bite aggressively.
Mosquitoes of this genus lay their eggs in rafts, like the Culex genus. Unlike Culex, when the eggs hatch, the larvae live underwater, breathing air through tubes they insert into the roots of aquatic plants, and don't turn into adults until the following year.
The most significant species in the U.S., Coquillettidia pertubans is found in most of the eastern states and some of the midwest. They're vicious biters, mostly in the evening and night, indoors and outdoors, but they'll also come out to bite during the day in damp, shady places.
There are fifteen species of this genus in the United States, in the south and east. Their eggs, which they lay on the ground, can withstand months of drying, then hatch quickly when floodwaters come.
Psorophora ciliata is a big yellow-brown mosquito found throughout the eastern U.S., called the "gallinipper." It's the bully of the mosquito world. The larvae are two or three times bigger than most, and they eat insects including other mosquito larvae. The adults bite aggressively day and night.
Psorophora columbiae (also called P. confinnis) typically lives in rice fields, though is found elsewhere. It's aggressive enough to swarm and kill livestock and drive people indoors.
Psorophora columbiae also likes rice fields or other places that flood occasionally. The eggs can grow to adults within a week in warm wet weather and the adults may live for a few weeks or a couple of months.
Psorophora cyanescens is a shiny blue color and is found over most of the south.
Psorophora ferox is bright bluish purple and prefers swampy woods in the south, west to Texas and north to Nebraska.
Psorophora signipennis lives in the midwest from Texas to North Dakota and has a painful bite.
A few other minor genera live in the U.S. One of them is unusual: a mosquito that doesn't bite! Toxorhynchites doesn't suck blood. Its big larvae actually eat other mosquito larvae, while the adults live on nectar and fruit. We could use some more of them!
Public domain images courtesy of the CDC.