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Common Blue / Brown Argus (UK) (1 Viewer)

Pete007

Well-known member
Although I enjoy photographing Butterflies I must confess I still struggle to identify Common Blue from Brown Argus with 100 % confidence so would appreciate any help or advice with the following photos.
Reading the field guide I have it refers to the the spot near the body on the underside of the forewing (Common Blue) & the figure of eight on the underside (Brown Argus).
However many of my photographs do not show the forewing extended far enough to show the diagnostic spot for Common Blue so I cannot always rely on this.

Photo 1 - I cannot decide if the two spots circled are close enough to constitute the figure of eight for Brown Argus and the spot arrowed does not always appear to be always present on some individuals.

Photo 2 - The Blue on the body suggests female Common Blue ?

Photo 3 - Compared to Photo 2 the lack of Blue near the body - Brown Argus

Photo 4 - The two spots circled are clearly separated and I would tend to lean towards Common Blue ?

Any help appreciated - Thanks
 

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This is a pair that brings people trouble some times, but it makes it easier the fact that you have few species in the UK.
#1: Common Blue, a female on dark brown ground colour (compare with your photo 4, where male, paler, and female, dark brown, are together: but these in photo 4 are not Common Blues, see below). It's easily confirmed as a CB also based on the same spots you encircled in photo #4 (aligned horizontally with body axis, contra vertically in the Argus spp). White fringes to the wings.
#2: Common Blue, female: blue scaling excludes Argus spp. White fringes to the wings.
#3: Brown Argus, a male. The abdomen shape (very narrow, with the tip aligned with wing border) and wing shape (pointed) make it a male, and as a male it would be blue if it were a Common Blue :)
#4: pair of Chalk-hill Blues: very pale ground colour on the male, reduced dark markings and tiny orange lunules; partially checkered fringes to the wings. The 2 spots your encircled allow you to exclude Argus spp. straight away (not always that clear) and then you have left Common, Adonis and Chalk-hill (these last 2 with checkered fringes).
Hope this helps.
 
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