Red threads on wings
 

Flying in an Alitalia MD80 I noticed three yellow triangles with red threads on the wing, similar to those used on sailboats to check the trim of the sail.
Can't imagine what they're for, especially because to check them, the pilots would have to lean outside in flight, something Alitalia pilots would never do as it would mess up their hair.
Can anybody enlighten me on the use of these strange things?

Where on the wing?

G

On the upper side of the wing (obviously..), about 1 metre from the fuselage, half a metre from the "bord d'attaque" (sorry don't know the word in English)

Pre-flight ice check
 

Do you remember a SAS MD-80 crashing at ARN a few years ago? The cause was clear ice on the upper wing detaching after take-off and damaging both engines.

To assist the crew in spotting clear ice (especially at night) the MD-80 now carries a small set of steps for the crew to stand on to see over the wing. If the red string is not visible and moving they need de-icing.

The leading edge I think.