QUESTION
Please explain the life cycle of a mosquito.
ANSWER
Mosquitoes are insects which go through several life stages, starting out as eggs, then hatching into larvae before developing into adults. Mosquito eggs are laid in slow-moving or stagnant pools of freshwater, to provide suitable habitat for the larvae once they hatch. Different species of mosquito prefer different water conditions; some prefer shaded areas, whereas some prefer more direct sunlight, and some mosquitoes even lay their eggs in very specific habitats, such as brackish water in estuaries. The way the mosquitoes lay their eggs can aid in identifying the genus of mosquito; some genera, such as Culex, lay rafts of many eggs, whereas Anopheles mosquitoes (the ones which transmit malaria to humans) lay their eggs singly. Larvae usually hatch from the eggs after a couple of days. These larvae are predatory, feeding on other aquatic insects and organisms, but themselves can also be eaten by fish, copepods and other creatures. Most larvae lay at an angle to the water surface and breathe through a specialized tube-like organ, known as a siphon, but Anopheles larvae lack the siphon and so much lay parallel to the water’s surface in order to breathe. Each larva must shed its skin (molt) four times, before reaching the stage where it forms a pupa. These four molts take anywhere from 7 to 14 days, depending on the water temperature. The pupa is just like a butterfly pupa – the mosquito does not feed and lays still in a cocoon as it develops into a adult. This process usually takes 2 days, after which the pupa splits and the adult emerges. The length of the full cycle is dependent on whether the conditions were optimal for that species of mosquito, and specifically based on temperature. Male adult mosquitoes usually live for about a week, feeding on nectar – they also possess very bushy antennae for seeking out females to mate with. Female mosquitoes have specialized mouthparts that allow them to feed on blood; they require the extra nutrients that blood provides in order to lay their eggs. The lifespan of a female adult depends on a number of environmental factors, but also her ability to get sufficient blood meals; in nature, they usually live 1-2 weeks.
A schematic of the life cycle is provided below:
Schematic of the mosquito lifecycle. Courtesy of Purdue University (Scott Charlesworth): http://extension.entm.purdue.edu/publichealth/insects/mosquito.html