One factor common to all mosquito species is that eggs are laid in association with free water or on a moist surface. Eggs are white when first deposited, darkening to a black or dark brown within 12-24 hours. Single eggs are about 1/50 inch (0.5mm) long, and those of most species appear similar when seen by the naked eye. Eggs are laid singly by some species, and others lay eggs together to form rafts. The incubation period (time between when eggs are laid and when they hatch) may vary considerably among species. Eggs of permanent-water mosquitoes where eggs are deposited on the water surface may hatch in 1-3 days depending on temperature. Floodwater species deposit their eggs on moist soil or another wet substrate and have a wide variation in incubation periods. These eggs will not hatch until submerged by rising water caused by rainfall, melting snow in the spring, or other floodwater. Depending on the species and conditions these eggs may hatch the next time they are flooded, as soon as ten days, or may not hatch until they are flooded a year or more later.
The larvae of all mosquitoes live in water and have four developmental periods or instars. These are called 1st, 2nd, 3rd, and 4th instars with each succeeding stage larger than the last. At the end of each instar, the larva sheds its skin by a process called molting. The larva is an active feeding stage. Larvae feed on particulate organic material in the water. The larvae of most species have a breathing tube and must occasionally come to the surface of the water to get oxygen. The total length of time that larvae spend in the larval stage depends on the species and the water temperature. Some can develop in as little as 5 or 6 days. Upon maturity the 4th instar larvae molts into the pupal stage.
Unlike most other insects, the mosquito pupa is very active, and, like the larva, lives in water. It differs greatly from the larva in shape and appearance. The pupa has a comma-shaped body divisible into two distinct regions. The front region consists of the head and thorax (cephalothorax) and is greatly enlarged. It bears a pair of respiratory trumpets on the upper surface. It must periodically come to the surface to get oxygen. The second region is the abdomen which has freely-movable segments with a pair of paddle-like appendages at the tip. Feeding does not take place during the pupal stage. The pupal stage only lasts for a few days and is the stage when all the larval tissues change into the adult tissues. The adult emerges directly from the pupal case on the surface of the water.
The adult mosquito is entirely terrestrial and is capable of flying long
distances. Both females and males feed on nectars which they use for
energy. Males and females mate during the first 3 to 5 days after they
have emerged. Females mate only once. Males generally live for only a
week. Only the females feed on blood, which is what is occurring when
they are biting. Females evidently gain little nourishment from blood
meals but need them in order to develop eggs. Many mosquitoes feed on
any warm-blooded bird or mammal. However, some prefer cold-blooded
animals. Some species also prefer birds and seldom feed on mammals,
which is the case with Culex spp. mosquitoes which are known to
transmit the West Nile virus (WNV). Unfortunately many species feed on a
wide range of warm-blooded mammals and humans are often attacked. Once
a female has completely engorged she flies to a shaded environment
until her eggs are completely developed, usually 3 to 5 days. Once the
eggs are developed the female is called a gravid female and she begins
to search for a desirable place to lay her eggs. If a female survives
her egg laying activities, she will very soon start searching for
another blood meal after which she will lay another batch of eggs. She
does not need to mate a second time. Generally a female will only live
long enough to lay 1 to 3 batches of eggs.
Most mosquito species are actively searching for a blood meal in the evening hours from just before dark until 2 to 3 hours after dark. During the daytime the females normally rest in cooler vegetated areas where the humidity is higher and they are protected from drying out. Females will often bite in the daytime if humans or animals invade the wooded areas where they are resting. However, Aedes albopictus is an aggressive biter which prefers to feed during the daylight hours and is often a nuisance in urban areas.
Ochlerotatus abserratus--Very common early spring to early summer mosquito pest of humans and other mammals. Larvae are found in temporary spring pools and margins of permanent waters in April. Readily bites in shaded areas during the day.
Ochlerotatus aurifer--Found occasionally in the spring and early summer. Vicious biting pest of humans and other mammals. Larvae are found in the spring in open marshes.
Ochlerotatus canadensis--Common late spring and summer mosquito. Fierce biting pest of humans and other mammals. Larvae are abundant in late spring and found occasionally during the summer in woodland pools, swamp borders and grassy hummock areas. This long-lived mosquito is the primary suspect in the transmission of heartworm to dogs and a possible suspect in the transmission of EEE from birds to humans.
Aedes cinereus--Common late spring and early summer mosquito pest of humans and other mammals. Larvae are found in late April and May in tussock and leather-leaf marshes.
Ochlerotatus excrucians--Very common mid spring and early summer mosquito pest of humans and other mammals. Larvae are found in a wide range of wetland habitats. This mosquito is a suspect in the transmission of heartworm to dogs.
Ochlerotatus sollicitans--Very common summer mosquito found primarily along the coast. This aggressive mosquito will bite on a hot sunny day and is known to fly long distances, so it occasionally turns up in our district. Larvae are found on the edges of salt marshes.
Ochlerotatus triseriatus--Common summer mosquito. A pest of humans and other mammals. Most of these larvae actually are found in old rimless tires, although some are found in other shaded artificial containers and in tree holes.
Ochlerotatus trivittatus--Common summer mosquito. Larvae are found in floodwater pools in both swamps and marshes. This pest is a persistent biter, and will even bite during the day.
Aedes vexans--Very common summer mosquito. This pest of humans and other mammals can have several generations each season, so the population may increase during the summer. Larvae are found in a wide variety of temporary pools and wetlands. This mosquito is a suspect in the transmission of EEE from birds to humans.
Anopheles punctipennis--Found occasionally in the spring and summer. This pest of humans and other mammals has a mildly annoying bite. The larvae are found in a wide variety of wetlands including permanent swamps and along the edges of ponds and slow moving streams.
Anopheles quadrimaculatus--Common Summer mosquito. A pest of humans and other mammals that readily enters houses and has a mildly annoying bite. The population increases during the summer. The larvae are found in clear water amongst low vegetation or floating debris, in permanent swamps, and along the edges of ponds and slow moving streams.
Culex pipiens and Culex restuans--Very common year round mosquitoes which primarily feeds on birds. It will readily enter a house, but is considered shy. It will typically only bite people when they are motionless, usually while they are sleeping. The larvae are found in water holding containers and in polluted waters. Culex pipiens are considered the primary vector of West Nile Virus and a potential vector of EEE.
Culex salinarius--Common summer mosquito. A fierce biting pest of birds, humans and other mammals which can have several generations in a summer, so the population may increase during the season. This mosquito is active all night. Larvae are found in both fresh and polluted grassy hummock areas of permanent water swamps.
Culiseta melanura--Common spring and summer mosquito. A bird- feeding mosquito that can have several generations per year, so the population may increase towards the end of the summer. Larvae are found in holes in the root structures of white cedar and red maple trees in swamps. This is an important mosquito species because it is believed to spread EEE virus through the bird population. This mosquito does not bite humans.
Coquillettidia perturbans--Very common mid-June to mid-August mosquito. An indiscriminate pest of birds, humans and other mammals that is known to be a vicious biter, and will readily enter homes. The larvae are unusual in that they are found attached to the submerged roots of cattails and a few other aquatic plants. This trait makes this species impervious to control using pesticides that are effective against larvae of other species. This mosquito is suspected in the transmission of EEE from birds to humans.
Culex territans, Culiseta morsitans, Uranotaenia sapphirinia-These are unimportant biters of birds and amphibians that are found in a variety of wetlands. Ur.sapphirinia are unusual because under a microscope they are an iridescent green.