A bit of reading (the Millennium Atlas and J. Thomas & R. Lewington) suggests it doesn't have a particularly strong migratory instinct so it's far less likely to make it over the channel like the LTB now regularly does. As to why it didn't make it here when there was still a land bridge connecting us to mainland Europe? Maybe it did and at some point, for whatever reason, it went extinct or maybe it was just too slow to make it before the Channel was formed?Jack Harrison wrote: ↑Sun Sep 11, 2022 4:28 pm Anyone with thoughts as to why ST Blue does not occur in UK (today)?
Jack
The ones captured in Dorset in the 1800's may have been part of a temporary colonisation, perhaps by a few gravid females making it over and finding suitable habitat.
The millennium Atlas also states "sightings of the Long-tailed Blue are still very rare and the apparent recent increase may simply reflect a greater intensity of recording, or more importation with fresh food stuffs. Although foodplants are widely available and breeding is possible, it seems the climate of Britain is unsuitable for colonization in the near future" written of course over 20 years now so who knows what will happen in the next few years!