Few animals on Earth evoke the antipathy that mosquitoes do. Their itchy irritating bites and nearly ubiquitous presence can ruin a backyard barbecue or a hike in the woods. They have an uncanny ability to sense our murderous intentions, taking flight and disappearing milliseconds before a fatal swat. And in our bedrooms, the persistent, whiny hum of their buzzing wings can irritate and keep us awake. Did you know? The red bump and itching caused by a mosquito bite is actually an allergic reaction.
Physical features and behavior
The slender elongated body of the adult is covered with scales, as are the veins of the wings. Mosquitoes are also characterized by long fragile-looking legs and elongated piercing mouthparts. The feathery antennae of the male are generally bushier than those of the female. The males, and sometimes the females feed on nectar and other plant juices and are known pollinators. In most species, however the females require the proteins obtained from a blood meal in order to mature their eggs. Different species of mosquitoes show preferences and, in many cases, narrow restrictions as to host animals.
The eggs are laid on the surface of water and hatch into aquatic larvae, or wrigglers, which swim with a jerking, wriggling movement. In most species, larvae feed on algae and organic debris, although a few are predatory and may even feed on other mosquitoes. Unlike most insects, mosquitoes in the pupal stage, called tumblers, are active and free=swimming. The pupae breathe by means of tubes on the thorax. The adults mate soon after emerging from their pupal cases. The duration of the life cycle varies greatly, depending on the species.
Mosquitoes are apparently attracted to host animals by moisture, lactic acid, carbon dioxide, body heat, and movement. The mosquito’s hum results from the high frequency of its wingbeats, and female’s wingbeat frequency may serve as a means of sex recognition.
Major species and diseases
Anopheles, the only known carrier of malaria, also transmits filariasis and encephalitis. Their egg laying usually occurs in water containing heavy vegetation. The female deposits her eggs singly on the water surface. Anopheles larvae lie parallel to water surface and breathe through posterior spiracular plates on abdomen instead of through a tube, as do most other mosquito larvae. The life cycle is from 18 days to several weeks.
The genus Culex is a carrier of viral encephalitis and, in tropical and subtropical climates, of filariasis. Egg laying may occur on almost any body of fresh water, including standing polluted water. The eggs, which float on the water, are joined in masses of 100 or more. The life cycle, usually 10 to 14 days, may be longer in cold weather.
The genus Aedes carries the pathogens that cause yellow fever, dengue, Zika fever, and encephalitis. Aedes usually lays eggs in floodwater, rain pools, or salt marshes. The eggs are capable to withstanding long periods of dryness. The short, stout larvae have a breathing tube containing a pair of tufts, and the larvae hand head down at a 45 degree angle from the water surface. The life cycle may be as short as 10 days or, in cool weather, as long as several months.
