Barely visible to the naked eye, mites have eight legs and a round body, and are seldom noticed until they have built up sufficient numbers to be a major infestation. They are not insects but are arachnids, related to spiders.
The typical mite emerges from its tiny egg in a dark crevice as a six-legged nymph, growing by a series of moults and acquiring another pair of legs in the process. Some species can survive starvation for up to six months.
Most houses have the House Dust Mite which lives on our mattresses, feeding on tiny particles of shed skin. The Furniture Mite occurs in damp upholstery. The Flour Mite infests damp cereals or pasta and causes “Grocer’s Itch”, in people who handle infested commodities.
Mange in pets is caused by mites; and the Itch Mite or Scabies Mite causes the disease of scabies by burrowing into the skin, causing an irritating rash. Bird Mites frequently enter houses from old nests of sparrows, starlings or house martins, or from poultry. Harvest Mites may bite people if brought in on the coats of dogs or on clothing. The most conspicuous mite that enters houses is the Red Spider Mite, a plant feeder which comes indoors in spring to seek egg-laying sites and again in autumn to hibernate.
Most “mosquitoes” seen in houses are in fact the harmless and unrelated Crane Fly. True mosquitoes are very much smaller but have a similar long thin abdomen, long thin legs and strongly veined wings. The head has large eyes and a prominent proboscis. There are two main groups; the Culicine mosquitoes sit with their bodies parallel to the ground, the Anopheline mosquitoes sit “nose-down” to the surface, and most have dark spots on their wings.
The commonest species indoors, often mis-identified as a gnat, is Culex pipiens. It does not bite but is almost indistinguishable from Culex molestus which does!
In the tropics, mosquitoes transmit yellow fever, filariasis, dengue fever and malaria. Even in Britain they cause those familiar itchy bites with a red swelling around them. Near estuaries or marshes, Anopheles maculipennis – a brownish species with small spots on its wings – is fairly common indoors. It bites readily, especially at dusk.
Mosquito eggs are laid in batches in stagnant water and the small brown larvae hang from the surface of the water, turning into comma-shaped aquatic pupae in four to ten days. Within a day or two the adult emerges with a thirst for human or animal blood. Only the females feed and require a blood meal before they can lay eggs. Adult female mosquitoes hibernate in dark corners of houses, sheds, cellars and other sheltered sites.