Identifying Confusion Species - The Fritillaries

Up until recently identifying Fritillaries in Northamptonshire was easy! That is because you were only really likely to see one species, the Silver-washed Fritillary, as Dark Green Fritillary sightings were quite rare. However, in recent years the Dark Green Fritillary has started to colonise the county and at some sites, particularly in the northeast, they have really gained a foothold and can often be recorded in good numbers. Dark Green Fritillaries are notoriously strong flyers and they have been recorded all over the county in recent years. Both the Fritillaries can be on the wing at the same time but there are a few differences which can make telling them apart quite easy. Both the Fritillaries, especially the Dark Green Fritillary, can be very active in the field so binoculars can prove very useful.

Fortunately, both the Silver-washed Fritillary and the Dark Green Fritillary are named after the patterns on their underwings so getting a good look at them is the easiest way of telling the species apart. The Silver-washed Fritillary, as its name suggests, has a streaked silvery wash on the underwings as seen in the photo below.

Silver-washed Fritillaries

The Dark Green Fritillary has a green wash and the hindwings have lots of large white spots too as seen in the photo below.

Dark Green Fritillary

However, due to the energy of these butterflies, seeing the underwings can be far easier said than done and more often than not only the upperwings can be seen well. Luckily once you know what to look for they are quite easy to tell apart. We’ll start with the Silver-washed Fritillary again. The males and females are slightly different so we will deal with those individually. The male is a bright orange colour with noticeable scent brands on the forewings that form distinct dark bands. Along the bottom of the wings you can see a double row of black spots, notice that the lower row of spots is separate from the dark outer margins.

Male Silver-washed Fritillary

The female Silver-washed Fritillary looks very similar to the male but it is slightly bigger, is a slightly duller orange colour and lacks the dark lines of the scent brand. Notice again that there is still the row of double spots running along the bottom of the wings which aren’t connected to the outer margins.

Female Silver-washed Fritillary

If you are really lucky you may even encounter a very special kind of female Silver-washed Fritillary known as the f. valezina. This stunning butterfly has a pearlescent silvery green base colour and a greenish wash to the underwings. If you see one of these it has to be a Silver-washed Fritillary as the Dark Green Fritillary doesn’t produce this form.

Female Silver-washed Fritillary f. valezina

Although the Dark Green Fritillary looks rather similar to the Silver-washed Fritillary there is one obvious way of telling them apart and it involves the outer margins of the wings again. If you look at the photograph below you can see that there is only one row of dots at the bottom of the wings and the markings that run along the bottom of the wings are all now joined to the outer margins forming small triangles.

Dark Green Fritillary