a large thorax with no legs, and a segmented abdomen. larvae breathe through spiracles located on their eighth abdominal segments, or through a siphon, so must come to the surface frequently. the larvae spend most of their time feeding on algae, bacteria, and other microbes in the surface microlayer. mosquito larvae have been investigated as prey of other dipteran flies. species such as bezzia nobilis within the family ceratopogonidae have been observed in experiments to prey upon mosquito larvae. they dive below the surface when disturbed. larvae swim either through propulsion with their mouth brushes, or by jerky movements of their entire bodies, giving them the common name of "wigglers" or "wrigglers". larvae develop through four stages, or instars, after which they metamorphose into pupae. at the end of each instar, the larvae molt, shedding their skins to allow for further growth. anopheles larva from southern germany, about 8 mm long culex larva and pupa culex larvae plus one pupa pupa as seen in its lateral aspect, the mosquito pupa is comma-shaped. the head and thorax are merged into a cephalothorax, with the abdomen curving around underneath. the pupa can swim actively by flipping its abdomen, and it is commonly called a "tumbler" because of its swimming action. as with the larva, the pupa of most species must come to the surface frequently to breathe, which they do through a pair of respiratory trumpets on their cephalothoraxes. they do not feed during this stage; typically they pass their time hanging from the surface of the water by their respiratory trumpets. if alarmed, say by a passing shadow, they nimbly swim downwards by flipping their abdomens in much the same way as the larvae do. if undisturbed, they soon float up again. after a few days or longer, depending on the temperature and other circumstances, the dorsal surface of its cephalothorax splits, and the adult mosquito emerges. the pupa is less active than the larva because it does not feed, whereas the larva feeds constantly. adult anatomy of an adult mosquito the period of development from egg to adult varies among species and is strongly influenced by ambient temperature. some species of mosquitoes can develop from egg to adult in as few as five days, but a more typical period of development in tropical conditions would be some 40 days or more for most species. the variation of the body size in adult mosquitoes depends on the density of the larval population and food supply within the breeding water. adult mosquitoes usually mate within a few days after emerging from the pupal stage. in most species, the males form large swarms, usually around dusk, and the females fly into the swarms to mate. males typically live for about 5–7 days, feeding on nectar and other sources of sugar. after obtaining a full blood meal, the female will rest for a few days while the blood is digested and eggs are developed. this process depends on the temperature, but usually takes two to three days in tropical conditions. once the eggs are fully developed, the female lays them and resumes host-seeking. the cycle repeats itself until the female dies. while females can live longer than a month in captivity, most do not live longer than one to two weeks in nature. their lifespans depend on temperature, humidity, and their ability to successfully obtain a blood meal while avoiding host defenses and predators. the length of the adult is typically between 3 mm and 6 mm. the smallest known mosquitoes are around 2 mm (0.1 in), and the largest around 19 mm (0.7 in). mosquitoes typically weigh around 5 mg. all mosquitoes have slender bodies with three segments: a head, a thorax and an abdomen. the head is specialized for receiving sensory information and for feeding. it has eyes and a pair of long, many-segmented antennae. the antennae are important for detecting host odors, as well as odors of breeding sites where females lay eggs. in all mosquito species, the antennae of the males in comparison to the females are noticeably bushier and contain auditory receptors to detect the characteristic whine of the females. adult yellow fever mosquito aedes aegypti, typical of subfamily culicinae. note bushy antennae and longer palps of male on left vs. females at right. the compound eyes are distinctly separated from one another. their larvae only possess a pit-eye ocellus. the compound eyes of adults develop in a separate region of the head. new ommatidia are added in semicircular rows at the rear of the eye. during the first phase of growth, this leads to individual ommatidia being square, but later in development they become hexagonal. the hexagonal pattern will only become visible when the carapace of the stage with square eyes is molted. the head also has an elongated, forward-projecting, stinger-like proboscis used for feeding, and two sensory palps. the maxillary palps of the males are longer than their proboscises, whereas the females' maxillary palps are much shorter. in typical bloodsucking species, the female has an elongated proboscis. the thorax is specialized for locomotion. three pairs of legs and a pair of wings are attached to the thorax. the insect wing is an outgrowth of the exoskeleton. the anopheles mosquito can fly for up to four hours continuously at 1 to 2 km/h (0.6–1 mph), traveling up to 12 km (7.5 mi) in a night. males beat their wings between 450 and 600 times per second. the abdomen is specialized for food digestion and egg development; the abdomen of a mosquito can hold three times its own weight in blood. this segment expands considerably when a female takes a blood meal. the blood is digested over time, serving as a source of protein for the production of eggs, which gradually fill the abdomen. feeding by adults aedes aegypti, a common vector of dengue fever and yellow fever typically, both male and female mosquitoes feed on nectar, aphid honeydew, and plant juices, but in many species the mouthparts of the females are adapted for piercing the skin of animal hosts and sucking their blood as ectoparasites. in many species, the female needs to obtain nutrients from a blood meal before it can produce eggs, whereas in many other species, obtaining nutrients from a blood meal enables the mosquito to lay more eggs. a mosquito has a variety of ways of finding nectar or its prey, including chemical, visual, and heat sensors. both plant materials and blood are useful sources of energy in the form of sugars, and blood also supplies more concentrated nutrients, such as lipids, but the most important function of blood meals is to obtain proteins as materials for egg production. when a female reproduces without such parasitic meals, it is said to practice autogenous reproduction, as in toxorhynchites; otherwise, the reproduction may be termed anautogenous, as occurs in mosquito species that serve as disease vectors, particularly anopheles and some of the most important disease vectors in the genus aedes. in contrast, some mosquitoes, for example, many culex, are partially anautogenous: they do not need a blood meal for their first cycle of egg production, which they produce autogenously; subsequent clutches of eggs are produced anautogenously, at which point their disease vectoring activity becomes operative. among humans, the feeding preferences of mosquitoes typically include: those with type o blood, heavy breathers, an abundance of skin bacteria, high body heat, and pregnant women. individuals' attractiveness to mosquitoes also has a heritable, genetically-controlled component. female mosquitoes hunt their blood host by detecting organic substances such as carbon dioxide (co2) and 1-octen-3-ol (mushroom alcohol, found in exhaled breath) produced from the host, and through visual recognition. mosquitoes prefer some people over others. the preferred victim's sweat smells more attractive than others' because of the proportions of the carbon dioxide, octenol, and other compounds that make up body odor. the most powerful semiochemical that triggers the keen sense of smell of culex quinquefasciatus is nonanal. another compound identified in human blood that attracts mosquitoes is sulcatone or 6-methyl-5-hepten-2-one, especially for aedes aegypti mosquitoes with the odor receptor gene or4. a compound called carboxylic acids in human body odor is also found to attract mosquitoes. a large part of the mosquito's sense of smell, or olfactory system, is devoted to sniffing out blood sources. of 72 types of odor receptors on its antennae, at least 27 are tuned to detect chemicals found in perspiration. in aedes, the search for a host takes place in two phases. first, the mosquito exhibits a nonspecific searching behavior until the perception of a host's stimulants, then it follows a targeted approach. most mosquito species are crepuscular (dawn or dusk) feeders. during the heat of the day, most mosquitoes rest in a cool place and wait for the evenings, although they may still bite if disturbed. some species, such as the asian tiger mosquito, are known to fly and feed during daytime. prior to and during blood feeding, blood-sucking mosquitoes inject saliva into the bodies of their source(s) of blood. this saliva serves as an anticoagulant; without it the female mosquito's proboscis might become clogged with blood clots. the saliva also is the main route by which mosquito physiology offers passenger pathogens access to the hosts' bloodstream. the salivary glands are a major target to most pathogens, whence they find their way into the host via the saliva. a mosquito bite often leaves an itchy weal, a raised bump, on the victim's skin, which is caused by histamines trying to fight off the protein left by the attacking insect. mosquitoes of the genus toxorhynchites never drink blood. this genus includes the largest extant mosquitoes, the larvae of which prey on the larvae of other mosquitoes. these mosquito eaters have been used in the past as mosquito control agents, with varying success. host animals mosquitoes feeding on a reptile many, if not all, blood-sucking species of mosquitoes are fairly selective feeders that specialise in particular host species, though they often relax their selectivity when they experience severe competition for food, defensive activity on the part of the hosts, or starvation. some species feed selectively on monkeys, while others prefer particular kinds of birds, but they become less selective as conditions become more difficult. for example, culiseta melanura sucks the blood of passerine birds for preference, and such birds are typically the main reservoir of the eastern equine encephalitis virus in north america. early in the season while mosquito numbers are low, they concentrate on passerine hosts, but as mosquito numbers rise and the birds are forced to defend themselves more vigorously, the mosquitoes become less selective of hosts. soon the mosquitoes begin attacking mammals more readily, thereby becoming the major vector of the virus, and causing epidemics of the disease, most conspicuously in humans and horses. multiple mosquitoes' withdrawal of blood from a host can add up to a large volume. in rare cases, heavy mosquito densities have directly killed livestock as large as cattle and horses. even more dramatically, in most of its range in north america, the main vector for the western equine encephalitis virus is culex tarsalis, because it is known to feed variously on mammals, birds, reptiles, and amphibians. even fish may be attacked by some mosquito species if they expose themselves above water level, as mudskippers do. in 1969 it was reported that some species of anautogenous mosquitoes would feed on the haemolymph of caterpillars although its nutritional value is questionable. other observations include mosquitoes feeding on cicadas and mantids. in 2014, it was shown that malaria-transmitting mosquitoes actively seek out some species of caterpillars and feed on their haemolymph, and do so to the caterpillar's apparent physical detriment. mouthparts mosquito mouthparts are very specialized, particularly those of the females, which in most species are adapted to piercing skin and then sucking blood. apart from bloodsucking, the females generally also drink assorted fluids rich in dissolved sugar, such as nectar and honeydew, to obtain the energy they need. for this, their blood-sucking mouthparts are perfectly adequate. in contrast, male mosquitoes are not bloodsuckers; they only drink sugary fluids. accordingly, their mouthparts do not require the same degree of specialization as those of females. externally, the most obvious feeding structure of the mosquito is the proboscis. more specifically, the visible part of