Blood-thirsty midges have us all sized up

TALL men and overweight women are more likely than their shorter and slimmer counterparts to fall prey to that scourge of the Scottish Highlands – the bloodsucking midge.

A study that examined the feeding preferences of the holiday-wrecking insects has also shown women seem to react more than men to the midges and suggests that susceptibility to their bites is hereditary.

The findings, which will be published in a scientific journal this week, represent the first time that researchers have found a relationship between body size and a person's attractiveness to midges.

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They said midge flight patterns could account for the insects attacking taller men first as most midges fly at a height of 2.8 metres above the ground.

When it came to women, the paper suggested larger figures would provide a "more substantial visual target for host-seeking midges". Fuller figures also gave out greater amounts of heat, moisture and chemicals that attract midges.

Scientists from Aberdeen University and the Rothamsted Research Institute in Hertfordshire have based their conclusions on a survey carried out amongst 325 athletes and spectators who attended the 2007 First Monster Challenge, a 120km team relay around the shores of Loch Ness.

The duathlon event attracted well-known names such as model Nell McAndrew, political adviser Alastair Campbell, rugby international Kyran Bracken, adventurer Ben Fogle and athlete Liz McColgan, who joined other dedicated runners and cyclists for one of the most popular endurance charity events in the sporting calendar.

But it was the clouds of midges that descended on athletes during drinks breaks and first aid stops that brought the event to the attention of a team of midge specialists from Rothamsted.

The following year they set up a study that included people at the event completing questionnaires that enabled the scientists to paint an accurate picture of midge behaviour.

Scientist Dr James Logan said: "We found that some people always got bitten more than others.

"Quite a small percentage (14.2 per cent] never got bitten. But what we found was that your size does have an effect.

"In men increasing height, made you more attractive to the midges.

"There was 'strong evidence' to show that a man standing 6ft 2in was more likely to be bitten than a man, who was only 5ft 7in.

"There appeared to be no evidence that a man's weight influenced his susceptibility.

"It is, therefore, possible that midges searching for a suitable host would be descending from above and would encounter taller people within a group first."

The susceptibility of women was influenced by their body mass index (BMI) – a measure of body fat based on a person's height and weight.

Women with a relatively high BMI were more likely to be bitten.

Logan's paper titled, "To bite or not to bite", which is to be published in the British Medical Council's Public Health Journal, also suggests a genetic factor in who gets bitten most. Previous studies have concluded some people produce chemicals in the skin that repel midges.

Logan's analysis supports this finding, saying that the repellent chemicals – produced naturally by the skin or by bacteria living within the skin – were likely to be under genetic control and could be passed from parents to children.

"There is a chance that this is hereditary. That is what this paper indicates, but this is something that we will be researching in the future," Logan said.

"We also found women's reaction to the bites was worse than men's, but that may be because women are more aware of their skin than men."

But there was bad news for those who believe in folk remedies to drive off midges. Over the years, various theories have been expounded about what substances discourage midge bites.

Eating strong-smelling food such as garlic has often been cited as a method of getting the better of midges. But that was discounted by the paper.

"There was no association between being bitten and the consumption of strongly-flavoured foods, eg garlic, chilli and onions," the paper said.

"This is contrary to popular belief as people commonly believe that garlic, in particular, makes you less attractive to biting insects."

Similarly, the theory that often emerges after boozy camping trips that alcohol consumption encourages midge attacks was not supported by Logan's research.

"Anecdotal evidence for this certainly exists in relation to midges. However, in our study we found no such association," the paper said.

Despite the study's conclusions, the midge was not too much of a distraction for one tall man, who took part in the 2008 First Monster Challenge.

Gavin Hastings, the 6ft 2in former British Lions captain, might have been a prime target. But he said: "I have a vague recollection that this study was going on.

"But I had more things to worry about than the wee Scottish midge on that day."

Twilight bloodsuckers by the million

ONLY five of the 37 species of midges in Scotland bite humans, and only female midges bite. The most vicious is the Highland midge. Midges are 3mm long and often form swarm clouds. In one study, five million midges were collected from an area of two square metres.

Midges find their prey by detecting miniscule changes in the levels of CO2 in the air, meaning everyone is at risk just by breathing. Midges can detect change in CO2 level from 200m away, and can also detect information about their prey like sex, diet, age and drug intake.

Midges are active between May and October, coinciding with the tourist season. Although peak midge times are at dawn and dusk, they are also present during the day. Midges bite to feed before laying their eggs. If undisturbed, a midge will drink for up to four minutes, although each midge will only consume 0.001ml of blood.