Thread subject: Diptera.info :: Fly bubble blowing
Posted by Cor Zonneveld on 14-10-2006 10:48
New theory on this behaviour. Over the last few cold bright days (air temp around 3-6'C) Every time the sun has actually been bright, I've found all the Scatphaga on one bush in the bright sun were bubbleblowing (around 3-4 of them). I don't normally see bubble blowing at that high frequency. Wonder if it's a way of warming up faster by letting the drop warm up in the sun and then sucking it back in again. Another reason for wondering this is normally flies seem to to sunbathe with their back to the sun (ie head away from the sun), whilst when they are bubble blowing they always seem to be facing the sun or at least at right angles to it, so the bubble is getting full sun.
I wonder about the physics of the process. Flies are generally some rather dark colour, so they take up solar heat easily. The fluid drops are mostly translucent, so any light just passes through them and little heat will be absorbed.
I attach a photograph of a small Sepsidae with a bubble. It was fully clouded weather, and on top of this, the fly would have been in full shadow if there were any sunshine!
So to me physics and some observations are not consonant with the heating-up-your-food hypothesis.
I'm sorry I cannot come up with something more positive...
Edited by Cor Zonneveld on 14-10-2006 11:09