Understanding the Mosquito Life Cycle
By Jennifer Kvamme, DVM
The mosquito is the main culprit (vector) responsible for the spread of heartworm disease in dogs and cats. Controlling the population of mosquitoes and preventing mosquito bites is part of preventing this deadly disease in dogs and cats. In order to control the population in neighborhoods and backyards, it helps to understand how the mosquito reproduces and develops.
There are four stages in the life cycle of a mosquito — egg, larva, pupa, and adult. The first three stages of the life cycle take place in water. Only when it reaches the adult stage does it become capable of flying. Every species of mosquito requires water to complete its life cycle. The difference is in the type of watery location where certain species lay their eggs — and in how they lay their eggs.
Species and Sex Differences
Some varieties of mosquitoes choose to lay large numbers of single eggs in moist soil that will eventually become flooded after the eggs are deposited. The eggs will hatch after the area has filled with water. Other species lay clumps (rafts) of eggs on the surface of standing bodies of water (tide pools, marshes, pastures, ponds, holes in trees, etc.) that are protected by weeds or structures. The rafts are very small, measuring only about a ¼ inch long, but with hundreds of eggs all together. The mosquitoes that lay eggs in flood plains are most active in early spring, while those that lay eggs on surface water are more active in the summer.
There are also differences in the feeding methods of the male and female mosquito. The female mosquito requires a blood meal from humans or animals in order to produce eggs. The male of the species feeds only from plants to get energy to survive. The lifespan of the female mosquito is about a month, depending on the environmental temperature, time of year, and humidity level. The lifespan of a male mosquito is only about one week.
The time required for a complete mosquito life cycle depends on the species of mosquito, as well as the environment in which it is developing. In cooler temperatures, it can take about two weeks for some species to complete a life cycle, but in warmer temperatures, this process can take place in ten days. There are some species that manage to complete a life cycle in as little as four days, or even extend it out to as long as a month, depending on the environmental conditions.
When the mosquito eggs are laid, the time it takes for them to hatch will depend on the species of mosquito and where the eggs are deposited. If the mosquito eggs are in moist soil waiting for water to flood the area, the eggs may lay dormant for up to a year before hatching. Mosquito eggs on water surfaces will usually hatch in just a few days, depending on environmental temperatures. The warmer the weather, the faster they will hatch.
When the mosquito eggs hatch, the larvae emerge and make their way to the surface for air. The larvae hang from the surface of the water, using breathing tubes, or siphons, to breathe. Some species of mosquitoes do not have siphons, but lay along the surface of the water to get air. The larvae eat particulate matter, such as algae, in the water, and shed their skins several times (molting) as they grow.
Larvae go through four development stages (called instars), increasing in size after each change. Depending on the species, the time spent as a larva will vary. Water temperature also plays a role in the speed of maturity. Larvae will develop anywhere from 5 to 14 days, after which it becomes a pupa.
The pupae continue to live in water and are very active. They must stay near the surface in order to breathe air from time to time. Unlike the larvae, the pupae do not eat. It is during the pupal stage that the mosquito develops into an adult. Development takes a few days, and the time necessary for the change to an adult depends on the species and the surrounding environmental temperature. Once development has occurred, the skin of the pupa splits open and the adult mosquito emerges. It remains on the surface of the water for the time it takes for the body to harden and dry.
Adult mosquitoes mate in the first few days after emerging. After drinking a blood meal, the female mosquito finds a shady location to develop her eggs over the next several days. After laying the eggs, the female mosquito may go on the hunt for another blood meal; she can then lay more eggs without the need to mate again. A female mosquito will lay up to several batches of eggs before completing her life cycle.