Mosquito

Mosquito — The mosquitos are insects which make up the family Culicidae. They have a pair of scaled wings, a pair of halteres, a slender body, and long legs. The females of most mosquito species suck blood (hematophagy) from other animals, which has made them one of the most deadly disease vectors known to man, killing millions of people over thousands of years and continuing to kill millions per year by the spread of diseases.

Length varies but is rarely greater than 16 mm (0.6 inch), and weight up to 2.5 mg (0.04 grain). A mosquito can fly for 1 to 4 hours continuously at up to 1–2 km/h travelling up to 10 km in a night. Most species are nocturnal or crepuscular (dawn or evening) feeders. During the heat of the day most mosquitos rest in a cool place and wait for the evenings. They may still bite if disturbed.

Both male and female mosquitos are nectar feeders, but the female is also capable of haematophagy (drinking blood). Females do not require blood for survival, but they do need supplemental protein for the development and laying of their eggs. Prior to sucking the blood, they inject a mild painkiller, which numbs the host to the pain from the “bite” (Note: mosquitos do not actually bite). The Toxorhynchites species of mosquito never drinks blood. This genus includes the largest of the extant mosquitos, the larvae of which are predatory on the larvae of other mosquitos. These mosquito eaters have been used in the past as mosquito control agents, with varying success.

The mosquito is composed of a head, thorax, and abdomen. The head contains the compound eye and proboscis. The proboscis is a piercing mouthpart used to suck blood from its prey. The mosquito’s head is mostly eye. Each eye is made up of many tiny lenses forming a compound eye. This type of eye allows a very big field of vision that easily detects movement. Next is the thorax. The thorax has one pair of wings and one pair of halteres. The thorax also has markings that are used in the identification of the mosquito. Then there is the abdomen or gut, which expands as it ingests its prey’s blood. The abdomen also has many markings that are used to identify the mosquito species.

In its life cycle the mosquito undergoes complete metamorphosis, going through four distinct stages: egg, larva, pupa, and adult, first described by the Greek philosopher Aristotle.

Female mosquitoes lay their eggs one at a time or together in rafts of a hundred or more eggs on the surface in fresh or any stagnant water. Anopheles and Aedes mosquitoes do not make egg rafts but lay their eggs separately. Culex, Culiseta, and Anopheles lay their eggs on water while Aedes lay their eggs on damp soil that is periodically flooded by water. Most eggs hatch into larvae in about 48 hours. A female mosquito may lay a raft of eggs every third night during its life span if it can find enough blood to develop the eggs.

Mosquitoes are a vector agent that carries disease-causing viruses and parasites from person to person without catching the disease themselves. Female mosquitoes suck blood from people and other animals as part of their eating and breeding habits. The female mosquito that bites an infected person and then bites an uninfected person might leave traces of virus or parasite from the infected person’s blood. The infected blood is injected through, or on, the “dirty” proboscis into the uninfected person’s blood and the disease is thus spread from person to person. When a mosquito bites, she also injects saliva and anti-coagulants into the blood which may also contain disease-causing viruses or other parasites. This cycle can be interrupted by killing the mosquitoes, isolating infected people from all mosquitoes while they are infectious or vaccinating the exposed population. All three techniques have been used, often in combination, to control mosquito transmitted diseases. Window screens, introduced in the 1880s, were called “the most humane contribution the 19th century made to the preservation of sanity and good temper.”