www.ukbutterflies.co.uk

Since reading the comments of Susie and others concerning Swallowtails,I have been thinking.....
In Switzerland where I have been recently,they were very common.In Croatia they were common.In France they are common.But they are different to our ones which seem to be confined to our Norfolk fens.On the continent they are just widespread and must have different foodplants and a different way of life.Perhaps the ones that used to be widespread in Southern and Central England were like the continental ones and for some reason they died out(collectors?).Would it not be worthwhile and aesthetically pleasing to try and introduce the continental strain to favoured sites in England and see what happens.After all they get far more snow,wind,hail and rain in Switzerland.
P.J.U.

I remember a thread, some time ago: viewtopic.php?f=14&t=6344&hilit=swallowtail that discussed the morphological differences between continental and British Swallowtails. It seems that nearly all of the 'rules' for distinguishing them fell down in some cases.

It appears strange that several species seem to find the English Channel/North Sea an impenetrable barrier, even when conditions in Britain seem similar. Introductions sometimes thrive for a while but then disappear. I suspect that this would happen with 'continental' Swallowtails, plus the possibility of inter-breeding with British Swallowtails, which would then confuse the distinction even further

Mike

"plus the possibility of inter-breeding with British Swallowtails, which would then confuse the distinction even further ". Indeed, a very serious crime against Britain's wildlife.
BWs, Neil

Perhaps it would be something to consider if the British swallowtails disappear as then it would be on a par with the large Blues.Some of us consider North Norfolk rather an outpost.
P.J.U.

I suspect the very mild, Atlantic climate of the UK is unsuitable for swallowtails, as it apparently is for Queen of Spain fritillaries. Continental swallowtails (like Queens) have made regular incursions to the British Isles but have never gained a foothold. The British swallowtails have clearly made evolutionary adjustments to survive in a very particular habitat (species living at the limits of their natural ecological tolerance often adapt to more narrowly specific conditions than their cousins in the main distribution - consider Glanville fritillaries, for example).

People often ask how Queens can survive just across the Channel if they can't in the UK; but of course, across the Channel their numbers can constantly be topped up from the huge stock in continental Europe. The Channel does seem to present a barrier to casual movement, even if occasional butterflies cross it. Swallowtails are good flyers but lack the powerful dispersal instinct of Queens so are even less likely to pop up in the UK.

I think any introduced, artificial colony of swallowtails in the UK would last a favourable season or two then die out. Like the Kipper, I would oppose the experiment!

Guy