THE age-old belief that midges bite some people more than others turns out to
be true鈥攁nd it鈥檚 all down to your sweat.
Researchers at the University of Edinburgh鈥檚 Centre for Tropical Veterinary
Medicine have uncovered evidence that the Highland biting midge (Culicoides
impunctatus) is particularly attracted to the sweat of certain individuals.
They told a meeting of the Royal Entomology Society in Aberdeen this week about
a series of daunting experiments carried out over the past few months鈥攖he
height of the summer midge season鈥攐n the island of Skye in Scotland.
Eight volunteers each exposed a forearm outdoors for between 3 and 5 minutes
and then counted their bites. There were notable differences between them. The
record went to one poor soul who was bitten 250 times.
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The researchers also placed extracts of sweat in midge traps overnight and
counted the midges in the morning. The sweat of one volunteer attracted 25,872
insects, significantly more than the others, and four times as many as traps
containing no sweat.
The results were confirmed by testing the attractiveness of different sweat
extracts in the laboratory. This involved measuring the electrical responses of
midge antennae, which are covered with 500 sensory hairs.
Mosquitoes have previously been shown to respond to two chemicals in human
sweat responsible for smelly armpits, methyl 2-hexenoic acid and 7-octenoic acid
(快猫短视频, 28 July, p 18).
Identifying what attracts insect pests
should enable scientists to develop more effective traps and repellents.
The Edinburgh researchers are now trying to isolate the chemicals in sweat
that have this effect on the midges. 鈥淚 have a vested interest,鈥� says team
member Sally Singh, 鈥渂ecause I get bitten to death.鈥�