www.ukbutterflies.co.uk

Why do some species of butterfly rub their forewings over their hindwings, first on one side, then the other? I have noticed this commonly with Small Blue and Green Hairstreak, but have not seen other butterflies do this, that I can recall.

I have noticed holly blues doing this as well as common blues... wonder if its lycaenidae (blues/hairstreaks) that do this only? I have never seen larger species doing this, only blues and green hairstreak, not sure if coppers do this.

They often seem to do this while nectaring so one could think that it is a simple pleasure reaction. I suspect it's something simpler - perhaps temperature maintenance. Any wing muscle action will generate heat, and taking on nectar will fuel that action. Or, it could be a means of pumping nutrients around the body - working the wing muscles compress the thorax in such a way as to circulate nectar around and help refuel. Maybe it's all three.

...or is it a way of drawing attention away from their heads?... A bird may go for the head of a butterfly unless confused by a moving outline towards the outside of the wings - the contrasting colour at the edge of the inner and outer surfaces may appear to get bigger and smaller as the insect moves and this may make it strike at the wings instead (or not strike at all if it then thinks it is a leaf moving in the wind rather than something edible)
Always does look like they are rubbing their hands together in preparation for a nice meal though

Is it both sexes? I've never noticed. Males might do it to rub the androconial patches and release scent.

Guy