Alameda County Mosquito Abatement District

education

MOSQUITO BIOLOGY – LIFECYCLE

All mosquitoes must have water to complete their lifecycle. This water can range in quality and it can be in any container imaginable. Adult mosquitoes show a distinct preference for the type of source in which to lay their eggs. They lay their eggs in places such as tree holes, salt marshes, sewage ponds, fishponds, rainwater ponds, buckets, containers, etc.

The mosquito goes through four separate and distinct stages of its lifecycle: egg, larva, pupa, and adult. Some species have naturally adapted to go through their entire life cycle in as little as four days or as long as one month. There are four common groups of mosquitoes living in the Bay Area. They are AedesAnophelesCulex, and Culiseta.

ms

Egg: Eggs are laid one at a time and can float on the surface of the water. In the case of Culex and Culiseta species, the eggs are stuck together in rafts of 100-300 eggs. A raft of eggs looks like a speck of soot floating on the water and is about 1/4 inch long and 1/8 inch wide. Anopheles and Aedes species do not make egg rafts but lay their eggs separately. Culex, Culiseta, and Anopheles lay their eggs on water while Aedes lay their eggs on damp substrate that will be flooded by water. Most eggs hatch into larvae within 48 hours of coming into contact with water.

Larva: Larvae, commonly called “wigglers” or “wrigglers,” live in water and breathe air from the surface. Most larvae have siphon tubes for breathing, however, Anopheles larvae do not have a siphon. They lay parallel to the water surface. Larvae feed on micro-organisms and organic matter in the water. They shed their skin four times growing larger after each molt. The stages between molts are called instars. When the 4th instar larva molts it becomes a pupa.

Pupa: Mosquito pupae are commonly called “tumblers.” The pupa is lighter than water and therefore floats at the surface. It takes oxygen through two breathing tubes called “trumpets.” When disturbed, it dives in a jerking, tumbling motion and then floats back to the surface. The pupal stage is a non-feeding stage. This is the time the mosquito turns into an adult. It takes about two days before the adult is fully developed. When development is complete, the pupal skin splits and the mosquito emerges as an adult.

Adult: Newly emerged adults rest on the surface of the water for a short time to allow itself to dry and all its parts to harden. The wings have to spread out and dry properly before it can fly. The feeding habits of adult mosquitoes are unique in that only the female bites. Male mosquitoes feed on plant juices. Depending on the species, female mosquitoes may prefer to feed on only one type of host or they can feed on a variety of hosts. Female mosquitoes feed to get a sufficient blood meal to develop eggs. However, some species of mosquitoes have developed the means to lay viable eggs without getting a blood meal.

The flight habits of mosquitoes depend on the species. Most domestic species remain fairly close to where they emerge, staying within a mile or two of their source. Some species, however, are often an annoyance far from their breeding place and have been recorded as far as 75 miles from their breeding source. The flight range for females is usually longer than that of males.

The life span of the adult mosquito usually depends on several factors: species, temperature, humidity, gender, and time of year. Males are typically shorter lived than females.