The Highland Midge: Scotland's Smallest, Most Famous Animal

Each major claim carries one of three labels. established means supported by primary records, official bodies or several independent reliable sources. shared means the core fact is sound but sources disagree on details, dates or interpretation. traditional means widely repeated but not traceable to a primary or independent source.

The midge's biology is well studied. Figures for midge numbers and their economic cost to tourism are often quoted but come from varied estimates and are labelled here. Folk remedies abound; few have been tested.

A tiny fly

established The Highland midge is a biting fly about 1.4 millimetres long, so small that it can pass through ordinary mosquito netting. Scotland has around 35 species of biting midge, but Culicoides impunctatus is the one responsible for most bites on people.

Why it bites

established Only female midges bite. They need protein from a blood meal to develop their eggs; males feed only on plant sugars. The first batch of eggs can be laid without blood, but later batches need it, and the females home in on their targets by sensing exhaled carbon dioxide, body warmth and body odour. Research from the London School of Hygiene and Tropical Medicine has found that some people are more attractive to midges than others. Dark clothing attracts them more than light.

established Midges cut the skin with saw-like mouthparts and inject saliva that stops blood clotting. The result is an itchy, swollen red lump that can last hours or days.

Where and when

established Midge larvae develop in damp, acidic soils and peat, so midges are most abundant in the wet, boggy landscapes of the west Highlands and islands. Adults are most active in still, humid, overcast weather and especially at dawn and dusk. They avoid bright sunshine and dry air, and cannot fly in winds of about 6 mph or more, which is why a breeze brings instant relief. The season runs from about mid-May to early September, peaking in the warm, damp middle of summer.

Living with midges

established Remedies range from chemical repellents such as DEET and picaridin, including Scottish-made brands, to citronella, nets, long sleeves and light-coloured clothing. Midges attack mainly when you stand still, so walking keeps most of them off. A daily midge forecast run by the repellent maker Smidge rates areas of Scotland on a scale from 1 (negligible) to 5 (nuisance). Commercial traps that release carbon dioxide can reduce numbers locally.

traditional Many folk remedies are recommended, such as bog myrtle, eating garlic or taking vitamin B, and a bath oil originally sold as a moisturiser became famous as a midge repellent among hillwalkers and soldiers. Evidence for most of these is anecdotal.

shared Midges are often said to cost the Scottish tourist industry hundreds of millions of pounds a year in lost visits. Such figures are widely repeated but come from rough estimates.

Why midges matter

established For all their nuisance, midges are a key part of the Highland food web. Their larvae and adults are eaten by birds, bats, frogs, fish and other insects, and their sheer numbers make them an important source of food in summer. Biting midges also matter to farmers, because some species can transmit livestock diseases such as bluetongue and African horse sickness. In Scotland they are not a significant carrier of human disease.

• Only female midges bite; males feed on plant sugars.
• A Highland midge is about 1.4 millimetres long.
• A breeze of about 6 mph is enough to ground them.
• Scotland has about 35 species of biting midge.
• There is a daily midge forecast in summer.
• Midges are an important food for bats and birds.

• Myth: All midges bite. Only the females bite, because they need a blood meal to develop their eggs. Males feed on plant sugars.
• Disputed: What midges cost Scottish tourism. Figures of hundreds of millions of pounds a year are widely repeated but come from rough estimates.
• Myth: Folk remedies such as bog myrtle, garlic or vitamin B keep midges away. Evidence for most of them is anecdotal, and few have been tested.
• Myth: Midges spread disease to people in Scotland. They are not a significant carrier of human disease here. They can transmit livestock diseases such as bluetongue.