Long-tailed Blue. Photo: Cath Walker

Cath Walker writes (on her Flickr Page – reproduced with permission):

The Curious Incident of the Unfamiliar Butterfly In the Kitchen

This morning I was slaving over a hot tax return form when Liz called me from the kitchen: “Do you want to see a butterfly?” Any sentence with “butterfly” in it gets me running, and so I ran to the kitchen to find this butterfly on a window pane. It looked like nothing I had ever seen before. Oh, the excitement!! I rushed (lots of fast exercise here) to get the camera and a glass jam jar to put the butterfly in so I could take its portrait before releasing it into the wild. Once released into the wild, ie the garden, it flew quickly away, so I only have indoor pictures to show.

Cath contacted our Records Officer, Bill Shreeves, who replied:

You are completely correct in your identification as a male Long -Tailed Blue & in your comment on Flickr that it is very rare. With global warming we are hopeful that in time it might become a regular inhabitant – it does after all occur commonly all over southern Europe & Asia, Africa & even Australia.

Our problem is that none of its stages seem to be able to get through the British winter. One of the first ever recorded in Britain was back in 1859 in Christchurch. After that it was seen fairly regularly but only in big numbers in 1945 & 1990.

It is a very bold migrant & in Asia steadily climbs the foothills of the Himalayas reaching Nepal at as high as 3,650 metres & reverse migrating to the lowlands!

In Dorset at least one has been reported yearly since 2005 except for 2006 & 2008. Yours is the only one so far for 2013.

Many of the records are in September but in 2007 there was one around the same time as yours – 14th October in that case – also found indoors. This makes me wonder whether the caterpillar or chrysalis might somehow have been brought inside.

The caterpillar feeds inside the pods of leguminous plants like everlasting peas, lentils & Bladder-senna. A famous example was in 1999 when butterflies found indoors were shown to have emerged from batches of mange-tout peas brought all the way from Kenya!

Not long ago I was invited to verify a Long Tailed Blue which suddenly appeared in a pantry. The householders had bought legumes some while back in an outdoor market and we hypothesised that they had contained a caterpillar or chrysalis.

If you can remember anything similar which might account for how yours came to be on a window pane in your kitchen please let me know!

Cath responded:

It seems most likely that the long-tailed blue must have entered our kitchen as a caterpillar or chrysalis in something, although I can’t think what, as most of the vegetables we buy are in shrink-wrapped supermarket packets and kept in the fridge. Home-grown vegetables enter the house accompanied by various insects – but then how would the caterpillar have got into them in the first place, if it’s a migrant from warmer climes? In the hot weather we have the kitchen door open all day, but even at the butterfly peak, only about one managed to fly into the kitchen. So in all, it’s a bit of a mystery how the long-tailed blue got here!