Biogents – Science for Your Protection –

House mosquitoes

In Central Europe, there are predominantly two species of mosquitoes found in human surroundings: the common house mosquito (Culex pipiens) and the banded mosquito (Culiseta annulata). Both have very similar ways of life, and often coexist. The common house mosquito is relatively inconspicuous: brownish with beige bands over the abdomen, and evenly coloured grey wings and dark legs.

The banded mosquito is larger and stronger, the abdomen is black and grey with light transverse markings, and the legs have white rings. There a few indistinct dark spots on the wings.

Both species lay their eggs in rafts of a few millimetres length that float on the surface of water in rain barrels, watering cans left standing around, clogged drains, ditches, garden ponds, or puddles. Each of these egg rafts comprises up to 350 eggs. Larvae that hatch from the eggs hang at the surface of the water, and breathe air through a snorkel-like siphon on their abdomen, but can go underwater in case of danger. As with all mosquito species, there are four larval stages with the largest one being up to one centimeter long. The larvae of house mosquitoes likewise feed on organic material, which they draw out of the water with their mandibles.

Egg raft, larva and pupae of house mosquitoes. Composition of details from the illustrations 43 and 44 in Réaumur R.A. (1738) Mémoires pour servir à l'histoire des insectes. Volume 4. Paris.
Egg raft, larva and pupae of house mosquitoes. Composition of details from the illustrations 43 and 44 in Réaumur R.A. (1738) Mémoires pour servir à l’histoire des insectes. Volume 4. Paris

House mosquito larvae can even live in sewage water and other highly polluted waters. The larvae and, accordingly, the mosquitoes they metamorphose into may be larger or smaller, depending on the supply of nutrients. The temperature of the water influences the speed of development: In warm summers, for example, the larvae may already complete their development within less than a week.

The fourth-stage larva changes into the so-called pupa, an animal resembling a comma that hangs at the surface of the water, and breathes air through two snorkel-like siphons at the front end. The larva metamorphoses into the adult animal inside the pupa. The speed, which this occurs with, is also dependent on temperature; it happens usually within just a few days. Female mosquitoes already develop their thirst for blood shortly after they hatch. After a successful sting, the nutrients in the blood meal are converted into eggs. After depositing the eggs, the female goes out in search of a host again. In this way, she is able to lay a number of egg rafts, thereby ensuring more and more offspring. (It may be of interest to know that the females feed on sweet plant juices and nectar just like the males in order to meet their energy requirement. The males, though, never drink blood.)

Whereas the males die in the autumn, female house mosquitoes escape increasingly cold temperatures by retreating into human dwellings among other places initially. They can become really annoying here once more. They survive the winter in cool and moist spots like cellars, storage rooms, stables, and barns. If there are sufficient heat and blood hosts in spots with collections of water (factory halls, subways), the development cycle may continue during the winter as well.

Click to enlarge image. Culex pipiens, illustrated by Ingeborg Schleip, Biogents