Adrian Flynn has reported a Long-tailed Blue to us, complete with photos. This is only the 10th Dorset record since 2010.
The most recent previous report was 12 September in 2016 on Boscombe Cliffs.
Adrian’s Long -Tailed Blue is earlier than all but one of our previous Dorset records, 16th June in 2009, as most of them have been in late August or September. The latest two were in October and November.
A lot of records both in Dorset and other counties have come from caterpillars imported in various legumes, including the pods of the Bladder Senna plant, lentils and mange-tout peas from countries such as Kenya.
We do not know whether Adrian’s Long-tailed Blue originated in imported goods; it is possible that it migrated here from France. The Long-tailed Blue is a very strong flyer and is distributed all over Europe and Asia. In India it regularly ascends into the foothills of the Himalayas in the dry season and back down to the lowlands for the wet season. It is known to migrate across many seas, so the English Channel is no obstacle.
2013 was the great migration year for Kent and Sussex, with a minimum of 65 different adults in Sussex alone. These produced small breeding colonies for a while and eggs were laid on Everlasting Peas. The caterpillars feed first on the flowers and then bore into the seed pods.
Our Records Officer, Bill Shreeves, observed that one of the photos sent in by Adrian possibly showed the butterfly attempting to lay an egg on his Sweet Peas, so Adrian has been asked to examine them closely for eggs or subsequently caterpillars. In theory, eggs laid now might go on to become adult butterflies in September. So far this species does not seem able to withstand English winters, but with global warming, this may change…