Facts About Cullicoides Impunctatus - The Scottish Highland Biting Midge
There are more than 1200 species of the biting midge throughout the world and 36 known species in the UK alone. While most of these insects need blood meals to survive, there are few that are as vicious and relentless as the Scottish Highland Midge, or Culicoides Impunctatus.
What is a midge
The Highland midge is a tiny insect with a wingspan of around just 1.4mm; it can be recognized by distinctive black spots on the wings which can be clearly seen when the midge is at rest or feeding. The midge seeks out its victim primarily by smell. They first detect through changes in temperature that there may be a suitable animal or human nearby. What really attracts their senses, however, is the combination of substances carried on exhaled breath of victims including carbon dioxide, lactic acid, water vapour and acetone, which acts as a powerful attractor almost like a pheromone.
As with their cousins the mosquito, it is only the female of the species which attack humans and animals to feed whereas the males obtain all the nutrition they require from plants. The females’ mouths are highly developed for the task of finding the blood meals they need to incubate their eggs. Their finely serrated mandibles work in a sawing motion to cut through layers of skin until they strike blood at which point they put these together to form a tube or straw through which they suck up the blood. A female C. Impunctatus will feed for around 4 minutes if left uninterrupted after which time, she will ‘go to ground’ and lose the urge to feed on blood again.
The main signal that the midge acts on to fly and bite is daylight. Most species are active only when radiation from the sun falls below 260 Watts per square metre (W/m2). This is why they are most commonly active around late evening into sunset and again around sunrise times. However, cloud cover and rainy weather during the day can also create such reduced radiation levels explaining why midges can be a real problem on damp, overcast days. Midges do not like strong bright sunlight or any wind speed over 5mph and they will quickly disappear in such conditions to take shelter in grass, heather and dark coloured tree trunks.
An adult flying midge has a lifespan of around 30 days. They emerge towards the end of May and into June, gathering in swarms to attract a mate. After copulation, the females turn their attention to acquiring the blood meal that will provide them with the nutrients that are essential for their eggs to mature. After securing the blood, they will find a suitable place – usually on damp ground or moss- where the eggs will mature and be laid within a few days in batches of 50 or more. The eggs hatch to larvae stage after 10-14 days and the larvae then burrow into the top few centimetres of soil where they will spend up to ten months (through autumn, winter and spring) feeding on other larvae and fungal spores. Between April and July that following year, the larvae form into pupae where they will stay just under the soil surface until they become fully formed adults and the cycle begins again. Moist conditions throughout this process are vital to the survival of the midge and a dry May and June can often have a huge impact on midge numbers, in the hottest years reducing the midge population by up to 90%!
Because the biting season of the Highland midge coincides with the busiest time of the year in terms of tourism and outdoor activities, there has been much research into methods to control the midge numbers and into repellent chemicals. Any attempts to control the numbers have been unsuccessful, perhaps no surprise when these creatures have been around so much longer than humans (Canadian scientists have identified 18 different midge species preserved in amber up to 75 million years old) When it comes to midge repellents though there have been varying degrees of success.
One of the oldest known and most successful ways to keep midges at bay is smoke – lighting a fire, burning incense, midge coils and even cigarette smoke all act as an effective deterrent.
The common herbal plant Mugwort (Artemisia vulgaris) translates from old-English as Midge Plant and along with Wormwood, of the same plant family, is affective when burnt or made into a lotion to apply to the skin.
Other natural plant extracts and oils which are proven to be effective insecticides include lavender, geranium, lemongrass, lemon, thyme, juniper, fennel, dill, eucalyptus, cedar and cypress. Many concoctions derived from mixtures of some of these plant oils have been used to varying degrees of success over the years.
The most popular midge repellent among outdoor pursuits fans in the Scottish Highlands in recent years has actually been a product that is not manufactured or marketed for such a purpose, but it has become so popular and seemingly effective for the task that many shops stock it as a midge repellent anyway. The product? – Avon’s Skin So Soft body lotion! It is unknown if there is actually an ingredient in this lotion that deters the midge or if it is just the case that the insects cannot bite through the oily product to the skin below.
(picture credit Brian MacLennan 2006)
Every year, millions of Highland midges cause major problems for thousands of people – tourists and locals alike. They have been written about for hundreds of years and people have tried hundreds of ways to control the midge population or reduce their chances of being bitten mercilessly while enjoying the beautiful Highland scenery. Research continues into these relentless insects and how to deal with them and their bites, but the likelihood (given how long they have been around for) is that we will never be completely rid of the Highland Midge and will just have to do what we can to make the Scottish summers bearable.
Hendry,G - Midges in Scotland - 1996 Mercat Press, Scotland - ISBN 1-873644-61-2