Mosquitoes

Everyone who has put his or her nose out-of-doors in the northern summer knows what a mosquito is. In Finland alone, 38 species of mosquitoes in five genera have been recorded, the most plentiful of which are the Aedes species, which include the most painful bloodsuckers. The species that attack humans vary from south to north, and can be recognized by their gray colour and black-and-white-striped abdomen. When they attack, however, we normally just kill them with a quick slap. Do we really know who they are?

Mosquitoes are spread all over the world, and are especially abundant in northern latitudes close to the treeline. A curious exception is Iceland where mosquitoes have never been recorded. Some species have a circumpolar distribution, while others occur either in Eurasia or North America. Not all attack humans – some specialize in other mammals or birds. Reindeer and caribou suffer from these flies so badly that they migrate to open areas that have fewer mosquitoes. This behavior allows them to avoid mosquito-borne diseases and parasites, which include tularemia, arboviruses, and various encephalitises.

Only female mosquitoes are bloodthirsty. Males sit in vegetation feeding on the nectar of flowers. After having a proper blood meal, the female seeks a suitable place for egg-laying. Depending on the species, this may be either a small pond or just moist ground where there is likely to be shallow water the following spring. The eggs are resistant to dry and cold conditions and hatch as the snow melts. A few species overwinter as adults and emerge early in summer. In the water, the tiny larvae catch small plankton and grow rapidly. Many aquatic invertebrates, like diving beetles, prey upon those larvae. Within two to three weeks of hatching, the larvae change into pupae, which also swim. After a few days, the pupae swim to the surface where it sheds its skin. The resulting imago sits for a short period on the empty pupal skin, drying out and hardening its wings. It then flies to nearby vegetation to hide. Adult mosquitoes are an important part of the diet of many northern insectivorous birds.

Juhani Itämies, Zoological Museum, Oulu University, Finland. From the CAFF publication, Arctic Flora and Fauna, http://www.caff.is