13th July 2025 - with so many different, but quite similar, 'blue' butterfly species around at the moment, here is a collection of photos that may help sort them out. Identification notes are included in the caption below each photo. The upper-sides are shown first, followed by the under-sides.
Whilst these species are sometimes found in gardens, they mostly prefer un-improved chalk grassland in places such as Granta Park, along the Roman Road or Fleam Dyke, or on Trumpington Meadows.
Upper-side of wings
Common Blue - male
Obvious bright blue, darkening towards the body. No wing spots.
Continuous white wing fringe (no dark bands)
Common Blue - female (see below)
Common Blue - female
More variable, from brown with blue patches, to mostly blue, but less bright than male.
Hind and fore wing edges have orange, and white-bordered black spots.
Like the male, continuous white fringe
Chalkhill Blue - male
Paler more silvery blue, strongest near the body turning to grey at the margin.
Dark wing spots, most obvious on the hind wing edge.
White fringe broken by brown bands (continuation of the dark veins)
Chalkhill Blue - female
Pale-mid brown - like other species, but often some blue flecks near the body.
Orange and black wing spots less pronounced. White wing fringe broken by brown bands
Brown Argus - male
More evenly dark brown, with complete absence of blue.
Bright orange and black spots (with no white) along edge of fore and hind wings, decreasing in size away from the body. Thin black margin to wings, with (largely) unbroken white fringe.
Brown Argus - female
Much like the male, dark brown but with brighter orange wing spots which continue evenly along
edges of both fore and hind wings. Thin black margin to wings, with (largely) unbroken white fringe.
Small Blue - male
Tiny - 20-25mm wingspan. Evenly brown rounded wings, with blue flecking near the body.
No spots. Less distinct white wing fringe.
Small Blue - female
Tiny and much like the male, but darker, more even brown with no blue.
No spots and more distinct unbroken white wing fringe.
Under-side of wings
Common Blue - male
Grey-brown with blue tinge nearest the body, with white-bordered black spots
and orange spots along wing edges. Unbroken white wing fringe.
Forewing has 'dog-paw print' of black spots, with 1-2 'cell spots' nearer the body
Common Blue - female
More evenly pale brown, with brighter orange spots, but otherwise like male.
Chalkhill Blue - male
Paler silvery with some brown, blue tinge towards body. Dark spots, including cell spot, within wing.
Inconspicuous black and orange 'spots', surrounded by white along wing edges.
White wing fringe broken with brown bands.
Chalkhill Blue - female
More evenly pale-mid brown making white-bordered black spots seem more distinct.
Indistinct orange spots. White wing fringe obviously broken by brown bands.
Brown Argus - female (male similar)
Male and female similar, with some females having more brightly-coloured orange spots.
Very similar to Common Blue in terms of colour and markings, but lacks the 'cell spot' on the forewing.
Small Blue - male and female similar
Much smaller, but underside otherwise similar to Holly Blue.
Pale, silvery blue with small dark spots. No trace of orange.
Holly Blue - male and female similar
Pale, silvery blue underside with dark spots. Very similar to, but much larger than, Small Blue.
Generally rests with closed wings, but if glimpsed, the upper side is always blue with darker edge.
Andy M
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