The Suffolk Argus
Which Lycaenid? A. Agestis (Brown Argus, top pie.), P.Argus (Silverstudded Blue, middle pie.), or P. icarus (Common Blue, bottom • .)f. ptc (Remember, reference to Argus in this article is Silver-studded Blue and not Brown Argus!). by SteveGoddard
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'Colo 'NoSp
May 1996
The 20th July last year was another· hot and sunny day. 1 was looking for butterflies in the Tunstall area when I came across a beautiful carpet of heather on Tunstall Common. Here I saw but two butterflies; one a Small Copper (Lycaena phlaeas) and the subject of this article, a Brown Argus (Aricia agestis) both nectaring on bellheather. I was able to watch this particular insect for what seemed to be a good five minutes during which time not for one moment did it show me its upper wings and for most of the time only its hindwing. This was a time when note-taking became invaluable. The following points were hastily noted: Colour/Markings: Ground colour a smokey brown with black spots encircled white, conspicuous on the forewing. Strong orange spots. No distinct blue although body hairs gave a hint of blue in the bright sunshine. Clear white 'jlttsh'on the hindwing. 'Colon'shaped black spots near outer-edge of the hindwing. No black spot nearer than half-way in to the body on forewing. No 'silverstuds' evident in black hindwing spots. Very fresh condition. Size: Noticeably smaller than adjacent Small Copper.
I( 7Beryl 'Pohnson
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by DouglasHammersley
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So what was it? Remember only the underside was visible. (I should emphasise that my experience with these species enabled me to focus on the 'text book'features but great patience was required particularly as far as the forewing spot was concerned!). Let us break down the notes: The date, 20th July. Right for P. argus with a flight period oflate June/July. Marginal for second brood of A. agestis which is usually late July to early
September and right for P. icarus which can be seen at any time in summer but late July to September brood is strongest. The habitat. Bell-heather is a prime area for P. argus. No sign of rock rose, storksbill or dove's foot cranesbill (A. agestis) or bird's-foot trefoil (P. icarus). Size. Smaller than Small Copper, this favours A. agesris or P. argus since P. icarus wingspan is similar (bur could be a small icarus!). White hindwing 'jlttsh'.Present on P. icarus and A. agesris bur not P. argus. (P. argus now looking unlikely). Silver-studs. Absence of silver-studs seems to rule our P. argus but they maybe extremely small (only very rarely are they absent altogether). Given normal circumstances, I should have seen something inthe bright sunshine. (P. argus looking more unlikely). No distinct blue. A. agestis will nor show any blue, on P. argus it is unlikely and on brown forms of P. icarus the blue could be so indistinct as to indicate none at all. What about the spots-in fact the key features? First, th·e forewing. 'No black spot nearer than half-way in to the body'. P. argus and A. agestis match this description. P. icarus has two spots near the base. We can now eliminate P. icarus bur what about the others. We need to look closely at the hindwing. The 'colon'(:) near the outer edge matches A. agestis only. In other blues this pair of black spots tend to be sideways on(..).
Therefore, this fresh Lycaenid in unexpected habitat on an early July date was Aricia agestis (Brown Argus). In addition to my notes I was able to take photographs to further confirm my identification later. A useful i.d. feature which could have helped further was the flight. Although it flew only briefly if I had been concentrating on the flight pattern I should have been able to detect a silvery reflection as the sun caught its underwings. This can only be mistaken for Small Blue (not a problem in Suffolk).
Summary When faced with underside views of these species focus on the forewing and hindwing spots. (Longer views will of course reveal other key features of P. argus particularly, silver-studs, broad orange band and absence of 'whiteflash' on the hindwing). It is A. -agestisand brown female P. icarus which cause the problems. 1. Forewing. A. agestis and P. argus show no black spots nearer than half-way in to the body, brown female P.icarus, has two such spots. 2. Hindwing. Only A. agestis has has a pair of black spots formed like a colon near the edge of the ourerwing.
N.B. Underside views may be required to distinguish female P. argus and A. agestis even when upper wings shown! I hope these notes prove helpful in recognising Brown Argus in particular, whose first brood will be on the wing from around mid-May.
We will.bepi.easedtopublishyour own observatiomor experienceswith thesespecies-Ed.
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