Mosquitoes are small ectoparasites that science says branched away from their relatives the flies approximately 220 million years ago. Represented by more than 500 species worldwide in 31 genera, mosquitoes bite host animals and suck out tiny amounts of blood. While biting a host animal, mosquitoes can transmit dangerous diseases like malaria, Dengue fever and West Nile virus. The insects have a vital reason to nibble; blood meal is required for reproduction in most species.
Mating and Eggs
Adult male mosquitoes consume only nectar; the female mosquitoes are the ones that bite. After feeding on blood meal and mating, female mosquitoes lay their eggs in the water. Generally, mosquitoes try to lay their eggs in small pools of water that do not contain fish. While mosquito populations may be high around large bodies of water, the egg-laying actually occurs in small, sheltered puddles of water along the edge. Some species deposit their eggs in groups, termed rafts, while other species lay their eggs individually in a number of spots.
Mosquitoes exhibit four life stages: egg, larva, pupa and adult. After one to four days, eggs hatch into larvae. They look like small, buoyant worms; colloquially they are called wigglers. The larvae live in the water, straining organic mater from the water column for sustenance, for up to 14 days. Mosquitoes then transform into pupae, somewhat akin to caterpillars' cocoon, except that pupae are mobile. The pupa stage persists for a few days until they transform into adults. The whole life cycle lasts about a week for males; females may live as long as a month. Mosquitoes in the aquatic life stages are consumed by fish, amphibians and larger insects; adults are hunted by bats and dragonflies.
The Role of Blood
Blood is a good food source of sustenance for adult female mosquitoes, rich in protein and packed with calories. Different mosquito species demonstrate varying details of biochemistry. Some, like Aedes aegypti, have been studied extensively in the lab. The exact physiological pathway connecting the ingestion of blood meal and egg development and subsequent reproduction is poorly understood. In a 2012 study at the University of California, Riverside, Alexander S. Raikhel discerned some of this pathway, including the importance of small, non-coding sections of RNA, termed microRNA, for egg development.
Diversity and Exceptions
Though mosquitoes share a surfeit of similarities, the diversity of the group produces a few strange adaptations. Most mosquito larvae feed on small organic bits of material, but larvae of the genus Toxorhynchites feed on other mosquito larvae. As adults, mosquitoes of this genus displays another interesting adaptation: The females consume nectar, rather than blood, just like the males do. Other mosquito genera display strange behaviors as well; Anopheles larvae crawl up plant stems to pull themselves out of the water in an effort to avoid predators.
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