Crataegi is a large butterfly and very gregarious, especially when puddling as 12529 shows - there were 50 or more puddling at one very small area, apparently no different to any other adjacent damp areas. When disturbed, they all fly up as if a flock of birds, and re-settle again in the same spot often landing on top of each other. It's spectacle you could watch for hours.

I can remember the first time I saw crataegi in the Queyras National Park in 2000 and I perched dangerously leaning over a cliff to get a postage-stamp size picture. It could have easily been my epitaph. Since then I have seen it in thousands in many places and the Dordogne in particular. It also seems to like the medium altitudes of many mountain areas, and I have found it in huge numbers between around 1000m and 1300m, although it does occur at higher altitudes.

It used to occur in south east England (Kent in particular) but disappeared around 1911 for reasons that are still not understood, but may be climatic, related to a series of poor wet summers.

It is quite an attractive butterfly when fresh but tends to have a rather waxy, yellowish and appearance as it loses its scales, when it can become almost transparent without apparently losing any of its flight ability. The male appears to almost pure white, whereas the female has a yellow-brown colouration.

observations

I believe this to be a male based on the strong discoidal mark at the external edge of the upf cell, even though the body shape suggests female.

a male. Note the tiny fly at the edge of the hindwing. Big fleas have little fleas, etc.

a large group of males puddling in sandy soil at the edge of a river. There appeared to be no difference in the soil, but all the crataegi were grouped in this one area, none outside it.

a mating pair, the female on the right being quite brown compared to the almost pure white male.