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  • brown argus

brown argus

Pictured: brown argus, Aricia agestis

Notes from Jenyns: Devils Ditch, in tolerable plenty. ~ Occurs also near Ely. ~ Gogmagog Hills. ~

200-year trend in Cambridgeshire: Increase.

Modern records

The phrase ‘tolerable plenty’ suggests that Jenyns found this species in reasonable numbers, at least in some years, and the rest of his notes show that it was present in a few different locations. The brown argus can still be seen in Cambridgeshire and it is now more widespread, but numbers fluctuate from year to year. Its spread is in part down to a recent change in foodplant, which has allowed this butterfly to colonise arable farmland.  It is thought that warmer temperatures allow the larvae to digest species of cranesbill, which are plants that occur as common weeds on field margins. In the past, the brown argus only fed on rockrose, which is confined to chalk grassland habitats such as found on Devils Dyke.

A very similar species, the northern brown argus, can also be found in the UK but only exists in Scotland and the north of England. Therefore, Jenyns would not have seen the butterfly flying throughout Cambridgeshire and the same is true today.

National records map

Brown argus national records map:

Northern brown argus national records map: