As we now seem to have the Large Tortoiseshell living in Dorset, at least for now, we need to work out how to tell it apart from the Small Tortoiseshell.
The Large is a generally duller butterfly than the Small, looking more orange than red-orange and with much less black on the rear wings. The Small has a very white/silver mark near the tip of the forewing which is lacking in the large.
The Large is a slightly bigger butterfly: 64-70mm wingspan, as opposed to 50-56mm.
It is very unlikely you will see this butterfly anywhere other than Portland in Dorset, but if you think you have found one, please report it via our online Record Form but it must be accompanied by a photo; you cannot attach a photo to the Record page, but you can send it in via our Photo Gallery, where a note linking it to your sighting would help us put the two together.
You are welcome to record a buttterfly using a different recording system (e.g. Living Record or iRecord), but note that these will not appear with the latest sightings on this website. All records come to the Dorset Branch of Butterfly Conservation for verification.
You can, however, enter it on our Record form and tick the box to say you are reporting it elsewhere as well, which will allow it to show in our records for now, but be ignored at the end of the year when all the records from everywhere are brought together.
We are excited to see what happens with the Large Tortoiseshell, which was definitely a resident butterfly in the UK if you look back fifty years or more. We should, however, say that releasing butterflies into the wild is not a very good idea, as a high proportion of the releases fail. You can see all the arguments in this article on the Butterfly Conservation HQ site.