The Brown Argus are Back!

Brown Argus (Aricia agestis), Bovingdon Brickworks, 10 May 2015

The Brown Argus (Aricia agestis) are back at the Brickworks! Well, one is...and hopefully more will soon emerge. After coming across the colony of 14 at the very end of August last year, it’s encouraging to find that a fresh adult, first generation, is on site. I’ve yet to locate the larval food plants but my flora knowledge is very limited so hopefully someone more clued up will have success. The area in which the adults are seen flying is the rough ground surrounding grid reference TL00800262. The food plants to look out for are:

Common Rock-rose (Helianthemum nummularium), which is used almost exclusively on calcareous grasslands. In other habitats it uses annual foodplants, mainly Dove's-foot Crane's-bill (Geranium molle) and Common Stork'-bill (Erodium cicutarium). There are also recent reports of egg-laying on Cut-leaved Crane's-bill (G. dissectum), Meadow Crane's-bill (G. pratense), and Hedgerow Crane's-bill (G. pyrenaicum).

The Brown Argus butterfly doesn’t seem to be rare across Herts and Middlesex, according to last year’s transect survey results. It was recorded at 26 of the 62 surveyed sites. And, in terms of abundance, it was on a par with the Small Copper. However, its habit of occurring only in small, compact colonies, travelling no more than a couple of hundred metres, at most, from where it emerged, means that the species can be rare at a local level. Ultimately, a total of only 30-35 Brown Argus butterflies were seen at the 9 nearest monitored sites to the Bovingdon Brickworks last year (excluding Aldbury Nowers, a Brown Argus stronghold), so, it is very good news to see it again:

Location Tring Park, Tring Miswell Lane, Tring Lakeside Nature Reserve, Finchley Heartwood Forrest, St Albans Stocker’s Lake, Rickmansworth Sherrards Park Wood, Welwyn Garden City       Roughdown Common, Hemel Hempstead Shrubhill Common, Hemel Hempstead Harpenden Common, Harpenden

Quantity      15 (18)    0    0    9 (9)    0    0    1 (3)    5 (5)    0

(The numbers in brackets represent the total including estimates for weeks missed during the survey)