World Mosquito Day, is observed annually on 20 August, to commemorate British doctor Sir Ronald Ross, who in 1897, discovered that female mosquitoes transmit malaria between humans. Ross is responsible for the annual observance, having declared shortly after his discovery that the day should be known as World Mosquito Day in the future. The London School of Hygiene & Tropical Medicine also holds Mosquito Day celebrations every year, including events such as parties and exhibitions, in a tradition dating back to as early as the 1930s.
Mosquitoes are small, midge-like flies that constitute the family Culicidae. Females of most species are ectoparasites, whose tube-like mouthparts (called a proboscis) pierce the hosts’ skin to consume blood. The word “mosquito” (formed by mosca and diminutive -ito is Spanish for “little fly”. Thousands of species feed on the blood of various kinds of hosts, mainly vertebrates, including mammals, birds, reptiles, amphibians, and even some kinds of fish. Some mosquitoes also attack invertebrates, mainly other arthropods. Though the loss of blood is seldom of any importance to the victim, the saliva of the mosquito often causes an irritating rash that is a serious nuisance. Much more serious though, are the roles of many species of mosquitoes as vectors of diseases. In passing from host to host, some transmit extremely harmful infections such as malaria, yellow fever, Chikungunya, West Nile virus, dengue fever, filariasis, Zika virus and other arboviruses, rendering it the deadliest animal family in the world.
The oldest known mosquito with an anatomy similar to modern species was found in 79-million-year-old Canadian amber from the Cretaceous. An older sister species with more primitive features was found in Burmese amber that is 90 to 100 million years old. Two mosquito fossils have been found that show very little morphological change in modern mosquitoes against their counterpart from 46 million years ago. These fossils are also the oldest ever found to have blood preserved within their abdomens.
Despite no fossils being found earlier than the Cretaceous, recent studies suggest that the earliest divergence of mosquitoes between the lineages leading to Anophelinae and Culicinae occurred 226 million years ago. The Old and New World Anopheles species are believed to have subsequently diverged about 95 million years ago. 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 change the taxonomy of the family. The two main subfamilies are the Anophelinae and Culicinae, these two subfamilies tend to transmit different diseases. Culicine species tend to transmit arboviral diseases such as yellow fever and dengue. Some species transmit various species of avian malaria, and various forms of filariasis, likemany Simuliidae do. Anopheline mosquitoes, sometimes bear pathogenic arboviruses, and are likely to transmit Human Malaria.
Mosquitoes are members of a family of nematocerid 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). In particular, the females of many species of mosquitoes are blood-eating pests and spread many dangerous diseases, whereas members of the similar-looking Chironomidae and Tipulidae are not. Many species of mosquitoes are not blood eaters and of those that are, many create a “high to low pressure” in the blood to obtain it and do not transmit disease. Also, in the bloodsucking species, only the females suck blood. even among mosquitoes that do carry diseases, not all of them transmit the same kinds of diseases, nor do they all transmit the diseases under the same circumstances; as their habits differ. So far Over 3,500 species of mosquitoes have already been described. Some mosquitoes that bite humans spread a number of infectious diseases affecting millions of people per year. Others that do not routinely bite humans, but spread animal diseases, may spread new diseases when their habitats are disturbed, for instance by sudden deforestation.