You’re sitting outside on a warm summer evening, watching a beautiful sunset but as soon as the sun goes below the horizon you feel something crawling over your eyelid, it stops and suddenly it bites. Before you know it you’re covered in tiny black biting midges, they crawl inside your clothes where they continue the onslaught, protected from your swiping  hands.

Sunset over Loch Kanaird from the summit of Meall Mor, Ullapool. ©Lorme Gill/SNH

This is a story heard all over Scotland, not just in the Highlands but in city gardens and parks too. There are actually around 35 different species of midge in Scotland, although only five of these will bite humans. The most infamous one, with a wingspan of just 1.4mm, is the Highland midge, or the Scottish biting midge, Culicodes impunctatus, which lives mainly in upland areas and the Highlands. But there’s also a midge that’s found in urban areas: this is the garden midge. It has a less painful bite than the Highland midge but is even more persistent.

So what exactly is a midge?
–  An invertebrate: it has no internal skeleton.
–  An arthropod: it has no external hard skeleton.
–  An insect: it has six jointed legs.
–  A fly: it has just one pair of wings.

Midges are only around in summer, what do they do for the rest of the year?
Midges have an interesting life cycle. Like butterflies and moths they have three very different forms after they hatch: first the larvae, a large-headed worm-like creature; then a pupa where the larvae’s body parts turn to mush and reorganise into a completely different form; then finally the adult midge.

Midge larva growing underground.

Adult midge.

The secret of the bite
Midges have a very specialised way of feeding. Whereas a mosquito pierces human skin with syringe-like mouthparts and sucks up the blood, a midge cuts the skin with scissor-like mouthparts and sucks up the pool of blood that forms by rolling its mouth into a short feeding tube. Meanwhile, its saliva stops the blood in the wound from clotting so it can keep on drinking to its heart’s content. It is this saliva that irritates the human body and causes the itchy lumps where we’ve been bitten.

Only the females bite. The male’s mouthparts are not strong enough to pierce skin so instead they feed on rotting plants or nectar from flowers. Females need the blood for energy to produce eggs. She can lay her first batch of eggs without feeding but she needs a blood meal before laying any further eggs.

A midge caught on a sundew growing at The Flows NNR, Forsinard. ©Lorne Gill/SNH/2020VISION

Midges seem to be such a pain, can’t we just get rid of the lot of them?
People who work in the outdoors can lose many days work because of midges. The tourist industry can also be affected if visitors have a bad midge experience on holiday. But aside from the fact that it would be almost impossible to control populations of the midge (each square metre of soil can contain up to 700 larvae), midges are an important part of the Scottish ecosystem. They provide food for bats, other invertebrates, birds and even carnivorous plants like sundews and butterworts. If you visit a bog, look out for midges stuck to the sticky hairs of the sundews.

What’s the best way to avoid being bitten?
Researchers have estimated that in an hour up to 40000 midges can land on an unprotected person. Midges are sensitive to light and only come out during the day if it’s cloudy or shaded. They don’t like wind, low temperatures or very dry conditions. To avoid being bitten, go inside around sunrise and sunset and when it’s cloudy or still. If you find yourself attacked by midges then cover your exposed skin, wear a midge net and use repellents that contain the chemical DEET. In the past Scots used bog myrtle, a plant that grows in bogs and moorland.

Bog myrtle, an old Scottish midge repellant. © Lorne Gill/SNH

Nobody escapes
Finally, midges have no respect for royalty. After a picnicking trip in Sutherland in 1872, Queen Victoria wrote in her diary that she was half devoured by midges.

Illustration by Chris Tyler.

This blog is taken from SNH’s All About series, devised for late primary and early secondary school children.