Today The Independent's Great British Butterfly Hunt turns its attention to a butterfly family that contains some of our rarest and most rapidly-declining species, the fritillaries.
An unusual name: and it stands for what these lovely insects all have in common, a chequered pattern of orange and black on their wings. The name fritillary comes from the Latin fritillus, meaning dice-box, although there is some dispute as to whether it refers to a chequered pattern on the side of such a box, or the dots on the dice themselves.
For several hundred years it has denominated a family of butterflies, and also a family of flowers bearing a similar chequered pattern, such as the snake's head fritillary, one of our scarcest and most beautiful plants, which is now found in only a few places (although it does grow in thousands in a famous "fritillary meadow" in Cricklade, Wiltshire).
The fritillary butterflies are spread across Britain, but some have become every bit as rare as their wildflower namesakes. There are 50 species in Europe; in Britain we have eight of them, and on Friday of last week The Independent went in search of the earliest ones to appear in the butterfly season, the pearl-bordered and the small pearl-bordered fritillaries, and the marsh fritillary.
All these insects are declining and have vanished from many of their former haunts, so to seek them out we went to a big wood near Salisbury which is run by a charitable conservation trust largely with the interests of butterflies in mind. We were not disappointed: in a carefully-managed scrubby clearing we found both pearl-bordered and small pearl-bordered fritillaries flying together, some of Britain's prettiest and scarcest insect species, fluttering in profusion in the warm May sunshine.
Later, in a damp clearing in another part of the wood, we found the even more attractive marsh fritillary, with its vivid wing pattern of orange and yellow stripes.
In the course of looking for fritillaries, we also managed to see five other new species not so far recorded this year: the large white and the green-veined white (which we profiled on 10 April) plus Adonis blue, small heath and painted lady (which will be profiled at a future date). So in our quest to see all 58 British breeding species of butterfly in a single summer, the eight new species bring our tally to 19; 39 to go.
The GreatBritishButterfly Hunt: Species 16, 17&18 (of 58)
In our sixth report, we profile three butterflies from the same family: the pearl-bordered and small pearl-bordered fritillaries lay their eggs on violets; the marsh fritillary lays on devil's-bit scabious. Apart from the Glanville fritillary, on the Isle of Wight, these are the earliest fritillaries to appear.
16. Pearl-bordered fritillary
Boloria euphrosyne. Orange-and-black chequerboard pattern. The first of the fritillaries to be seen, visible from mid-April. The "pearls" are the row of seven silvery dots on the edge of the lower underwing; it has a single row, whereas the small pearl-bordered has two.
Larval food plants: violets (principally the common dog violet) among dead bracken or leaf-litter, which absorb the sun's heat to provide a warm microclimate.
Where seen: woodland glades, clearings, edges and rides, where violets grow amidst the bracken and scrub. Flutters low over the ground.
Conservation status: One of Britain's most-threatened butterflies. Seventy per cent decrease since 1976; now found in scattered colonies mainly in the west.
17. Small pearl-bordered fritillary
Boloria selene. Smaller and darker than its relative the pearl-bordered, with a different underwing pattern, it appears three weeks later, from early May onwards. Recent research revealed it has a very different ecology, being much better able to tolerate cooler and more open conditions.
Larval food plants: violets, growing in grassy clearings and rides.
Where seen: open areas like mountain grasslands, moors. Widely distributed in the West Country, Wales and Scotland.
Conservation status: declining steeply, down 65 per cent since 1976.
18. Marsh fritillary
Euphydryas aurinia. One of the brightest of Britain's butterflies, being striped rather than spotted or chequered, with orange, yellow and black bands contrasting vividly on its wings. It is mainly a butterfly of wet grassland, and the drainage of many fields for the intensification of farming, especially in eastern England, has led to a major decline in its numbers.
Larval food plants: devil's bit scabious (a wild flower with a pale blue head).
Where seen: damp meadows and grasslands in the west.
Conservation status: a huge plunge in numbers of nearly 70 per cent before the 1980s, but careful conservation work has brought it back, with a 48 per cent increase since 1983.