mosquito mosquito mosquitoes (or mosquitos) are approximately 3,600 species of small flies comprising the family culicidae (from the latin culex meaning "gnat"). the word "mosquito" (formed by mosca and diminutive -ito) is spanish for "little fly". mosquitoes have a slender segmented body, one pair of wings, one pair of halteres, three pairs of long hair-like legs, and elongated mouthparts. mosquitotemporal range: late cretaceous (cenomanian) – recent female culiseta longiareolata scientific classification kingdom: animalia phylum: arthropoda class: insecta order: diptera superfamily: culicoidea family: culicidaemeigen, 1818 subfamilies anophelinae culicinae diversity 41 genera the mosquito life cycle consists of egg, larva, pupa, and adult stages. eggs are laid on the water surface; they hatch into motile larvae that feed on aquatic algae and organic material. these larvae are important food sources for many freshwater animals, such as dragonfly nymphs, many fish, and some birds such as ducks. the adult females of most species have tube-like mouthparts (called a proboscis) that can pierce the skin of a host and feed on blood, which contains protein and iron needed to produce eggs. thousands of mosquito species feed on the blood of various hosts ⁠— vertebrates, including mammals, birds, reptiles, amphibians, and some fish; along with some invertebrates, primarily other arthropods. the mosquito's saliva is transferred to the host during the bite, and can cause an itchy rash. in addition, many species can ingest pathogens while biting, and transmit them to future hosts. in this way, mosquitoes are important vectors of parasitic diseases such as malaria and filariasis, and arboviral diseases such as yellow fever, chikungunya, west nile, dengue fever, and zika. by transmitting diseases, mosquitoes cause the deaths of more people than any other animal taxon: over 700,000 each year. it has been claimed that almost half of the people who have ever lived have died of mosquito-vectored disease, but this claim is disputed, with more conservative estimates placing the death toll closer to 5% of all humans. mosquitoes cannot live or function properly when the air temperature is below 10 degrees celsius (50 degrees fahrenheit). they are mostly active at 15–25 degrees celsius (59–77 degrees fahrenheit). fossil record and evolutionary history the oldest known mosquitoes are known from amber dating to the late cretaceous. three species of cretaceous mosquito are currently known, burmaculex antiquus and priscoculex burmanicus are known from burmese amber from myanmar, which dates to the earliest part of the cenomanian stage of the late cretaceous, around 99 million years ago. paleoculicis minutus, is known from canadian amber from alberta, canada, which dates to the campanian stage of the late cretaceous, around 79 million years ago. priscoculex burmanicus can be definitively assigned to anophelinae, one of the two subfamilies of mosquitoes alongside culicinae, indicating the split between these two subfamilies occurred over 99 million years ago. molecular estimates suggest that the split between the two subfamilies occurred 197.5 million years ago, during the early jurassic, but that major diversification did not take place until the cretaceous. the mosquito anopheles gambiae is currently undergoing speciation into the m(opti) and s(avanah) molecular forms. consequently, some pesticides that work on the m form no longer work on the s form. over 3,500 species of the culicidae have already been described. they are generally divided into two subfamilies which in turn comprise some 43 genera. these figures are subject to continual change, as more species are discovered, and as dna studies compel rearrangement of the taxonomy of the family. the two main subfamilies are the anophelinae and culicinae, with their genera as shown in the subsection below. the distinction is of great practical importance because the two subfamilies tend to differ in their significance as vectors of different classes of diseases. roughly speaking, arboviral diseases such as yellow fever and dengue fever tend to be transmitted by culicine species, not necessarily in the genus culex. some transmit various species of avian malaria, but it is not clear that they ever transmit any form of human malaria. some species transmit various forms of filariasis, much as many simuliidae do. taxonomy mosquito head family mosquitoes are members of a family of nematoceran flies: the culicidae (from the latin culex, genitive culicis, meaning "midge" or "gnat"). superficially, mosquitoes resemble crane flies (family tipulidae) and chironomid flies (family chironomidae). subfamilies anophelinae culicinae genera mosquitoes have been classified into 112 genera, some of the more common of which appear below. aedeomyia aedes anopheles armigeres ayurakitia borachinda coquillettidia culex culiseta deinocerites eretmapodites ficalbia galindomyia haemagogus heizmannia hodgesia isostomyia johnbelkinia kimia limatus lutzia malaya mansonia maorigoeldia mimomyia onirion opifex orthopodomyia psorophora runchomyia sabethes shannoniana topomyia toxorhynchites trichoprosopon tripteroides udaya uranotaenia verrallina wyeomyia species over 3,500 species of mosquitoes have thus far been described in the scientific literature. genomics an analysis by matthews et al. 2018 suggests mosquito species all carry a large and diverse number of transposable elements. morphology as true flies, mosquitoes have one pair of wings, with distinct scales on the surface. their wings are long and narrow, as are their long, thin legs. they have slender and dainty bodies of length typically 3–6 mm, with dark grey to black coloring. some species harbor specific morphological patterns. when at rest they tend to hold their first pair of legs outward. they are similar in appearance to midges (chironomidae), another ancient family of flies. tokunagayusurika akamusi, for example, is a midge fly that looks very much like mosquitoes in that they also have slender and dainty bodies of similar colors, though larger in size. they also have only one pair of wings, but without scales on the surface. another distinct feature to tell the two families of flies apart is the way they hold their first pair of legs – mosquitoes hold them outward, while midges hold them forward. life cycle image of pitcher plant mosquito wyeomyia smithii, showing segmentation and partial anatomy of circulatory system overview like all flies, mosquitoes go through four stages in their life cycles: egg, larva, pupa, and adult or imago. the first three stages—egg, larva, and pupa—are largely aquatic. each of the stages typically lasts 5 to 14 days, depending on the species and the ambient temperature, but there are important exceptions. mosquitoes living in regions where some seasons are freezing or waterless spend part of the year in diapause; they delay their development, typically for months, and carry on with life only when there is enough water or warmth for their needs. for instance, wyeomyia larvae typically get frozen into solid lumps of ice during winter and only complete their development in spring. the eggs of some species of aedes remain unharmed in diapause if they dry out, and hatch later when they are covered by water. eggs hatch to become larvae, which grow until they are able to change into pupae. the adult mosquito emerges from the mature pupa as it floats at the water surface. bloodsucking mosquitoes, depending on species, sex, and weather conditions, have potential adult lifespans ranging from as short as a week to as long as several months. some species can overwinter as adults in diapause. breeding in most species, adult females lay their eggs in stagnant water: some lay near the water's edge while others attach their eggs to aquatic plants. each species selects the situation of the water into which it lays its eggs and does so according to its own ecological adaptations. some breed in lakes, some in temporary puddles. some breed in marshes, some in salt-marshes. among those that breed in salt water (such as opifex fuscus), some are equally at home in fresh and salt water up to about one-third the concentration of seawater, whereas others must acclimatize themselves to the salinity. such differences are important because certain ecological preferences keep mosquitoes away from most humans, whereas other preferences bring them right into houses at night. some species of mosquitoes prefer to breed in phytotelmata (natural reservoirs on plants), such as rainwater accumulated in holes in tree trunks, or in the leaf-axils of bromeliads. some specialize in the liquid in pitchers of particular species of pitcher plants, their larvae feeding on decaying insects that had drowned there or on the associated bacteria; the genus wyeomyia provides such examples — the harmless wyeomyia smithii breeds only in the pitchers of sarracenia purpurea. some of the species of mosquitoes that are adapted to breeding in phytotelmata are dangerous disease vectors. in nature, they might occupy anything from a hollow tree trunk to a cupped leaf. such species typically take readily to breeding in artificial water containers. such casual puddles are important breeding places for some of the most serious disease vectors, such as species of aedes that transmit dengue and yellow fever. some with such breeding habits are disproportionately important vectors because they are well-placed to pick up pathogens from humans and pass them on. in contrast, no matter how voracious, mosquitoes that breed and feed mainly in remote wetlands and salt marshes may well remain uninfected, and if they do happen to become infected with a relevant pathogen, might seldom encounter humans to infect, in turn. eggs and oviposition electron micrograph of a mosquito egg mosquito habits of oviposition, the ways in which they lay their eggs, vary considerably between species, and the morphologies of the eggs vary accordingly. the simplest procedure is that followed by many species of anopheles; like many other gracile species of aquatic insects, females just fly over the water, bobbing up and down to the water surface and dropping eggs more or less singly. the bobbing behavior occurs among some other aquatic insects as well, for example mayflies and dragonflies; it is sometimes called "dapping". the eggs of anopheles species are roughly cigar-shaped and have floats down their sides. females of many common species can lay 100–200 eggs during the course of the adult phase of their life cycles. even with high egg and intergenerational mortality, over a period of several weeks, a single successful breeding pair can create a population of thousands. an egg raft of a culex species, partly broken, showing individual egg shapes some other species, for example members of the genus mansonia, lay their eggs in arrays, attached usually to the under-surfaces of waterlily pads. their close relatives, the genus coquillettidia, lay their eggs similarly, but not attached to plants. instead, the eggs form layers called "rafts" that float on the water. this is a common mode of oviposition, and most species of culex are known for the habit, which also occurs in some other genera, such as culiseta and uranotaenia. anopheles eggs may on occasion cluster together on the water, too, but the clusters do not generally look much like compactly glued rafts of eggs. in species that lay their eggs in rafts, rafts do not form adventitiously; the female culex settles carefully on still water with its hind legs crossed, and as it lays the eggs one by one, it twitches to arrange them into a head-down array that sticks together to form the raft. aedes females generally drop their eggs singly, much as anopheles do, but not as a rule into water. instead, they lay their eggs on damp mud or other surfaces near the water's edge. such an oviposition site commonly is the wall of a cavity such as a hollow stump or a container such as a bucket or a discarded vehicle tire. the eggs generally do not hatch until they are flooded, and they may have to withstand considerable desiccation before that happens. they are not resistant to desiccation straight after oviposition, but must develop to a suitable degree first. after that, they can enter diapause for several months if they dry out. clutches of eggs of the majority of mosquito species hatch as soon as possible, and all the eggs in the clutch hatch at much the same time. in contrast, a batch of aedes eggs in diapause tends to hatch irregularly over an extended period of time. this makes it much more difficult to control such species than those mosquitoes whose larvae can be killed all together as they hatch. some anopheles species do also behave in such a manner, though not to the same degree of sophistication. larva anatomy of a culex larva the mosquito larva has a well-developed head with mouth brushes used for feeding,