There are several factors beyond just what a butterfly looks like which can help you identify it.
Where is it in the UK?
Dorset is lucky in having a lot of butterfly species, but there are some not found in the County. Only Dorset species are covered in our Species pages.
What sort of habitat is it in?
Although some butterflies can be found in a wide variety of habitats, some are quite specialist. You will not see a Silver-studded Blue in a wood, or a Silver-washed Fritillary in wide open grassy fields. See the ‘habitat’ section of our Species pages.
What is the time of year?
This is very important. A lot of species are only on the wing for a few weeks of the year. See the ‘flight times’ section for each species to tell you if it is likely to be flying.
What size is it?
It is difficult to convey size in photographs, though we have included ones which particularly help in this respect where we have them. It is easy to assume that all butterflies are the size of the ones you see in you garden, but these are among the largest in the UK and small ones are very much smaller. We describe each in the text as ‘large’, ‘medium’ or ‘small’; if you want to see more exact sizes, go to our Sizes page.
There is not necessarily any consistency between the size description in the name. The Small White is smaller than the Large White, but a lot bigger than the Small Copper.
We recommend the FSC ‘Guide to the Butterflies of Britain’ pamphlet, which pulls out so you can see all British butterflies at once, with the pictures being life size, so you can see how various species compare.
The ‘foodplant’ we quote in the butterfly descriptions is that eaten by the species’ caterpillar, which is different to the flowers used by the adults to gain nectar. It may, however, give you a clue to the species’ identification, as the females will spend time around the foodplant when they are ready to lay their eggs, and the males are attracted to the females in the hope they have not yet mated.
It’s brown, why is it listed as a Blue?
Do not expect the name to necessarily reflect the colour. In the Whites you have the Brimstone, whose male is bright yellow; in the Blues, all the females are brown and the Marbled White is a Brown!
It doesn’t look quite right…
Just to make life interesting, any species may have a variation on the normal, called an aberration. Some of these aberrations are frequent enough to be have their own names. If you want to browse these, see the Cockayne Collection on our Links page . You also need to realise that all butterflies fade with time, as they lose scales off their wings; very faded specimens can be impossible to identify.
It’s mainly right, but has marks across the forewings
Some male butterflies have sex-brands, which are organs producing scent to help it to attract a female of its own species. These are very clear on some butterflies, but more mixed in with the general markings on others. Gatekeepers are a species where they show up well. Females may also be identifiable by having fatter bodies, as they are carrying eggs.
It’s got some odd red-coloured dots on the body
These are probably parasitic mites called Trombidium. They mainly affect the Small Skipper, Common Blue, Marbled White, Gatekeeper and Meadow Brown, but will affect other species, as can be seen in the photo below. They do not usually seem to harm the butterfly.
Is it a moth?
A colourful ‘butterfly’ may actually be a moth. There are quite a few moths which fly in the daytime, and some of them are very attractive.