When a colleague came to this site 12 months ago and reported multiple sightings I decided to include it on my own national butterfly agenda again this year. The best place on the English mainland for Glanville Fritillary attracts many visitors. Since an unofficial release in 2011 the outcome has been rather more successful than previous re-introductions, all of which were short-lived, whilst here things are still thriving some 10 years on.

I myself last visited the colony six years ago. That post in my 2015 British Butterflies series has been by far and away the most referred to in this journal, being viewed over 300 times more than any other. But it actually said very little as we only found one individual that day, and so has now been removed. This new one is intended to be my English reference for what is clearly a very popular item.

Hutchinson’s Bank (TQ381616) is owned by the London Borough of Croydon and managed by the London Wildlife Trust and the Downlands Partnership. The reserve covers a dry valley slope that is the largest area of chalk grassland remaining in Greater London. It supports a diverse flora and up to 28 butterfly species. From the end of Farleigh Dean Crescent (CR0 9AD), off Featherbed Lane a track leads through a hillside cutting that is the prime spot for viewing Glanvilles. On rising early today, as is usual at this time of year, I decided to beat the M25 rush hour and so arrived at around 8:30am. Five other observers were there ahead of me.

As the day began to warm up a first trip target was called at around 9:10am. The “early shift” were all genuine butterfly enthusiasts so we gave each other space, shared the picture opportunity and got on well. But mission having at least been accomplished I still preferred to wander off and explore elsewhere. Eventually re-entering the cutting from the other end, two or three Glanville Fritillary were by then active and for a while I had them all to myself.

At that stage of the day the butterflies were more inclined to settle open-winged to bask, as these pictures (above) show. They were very low flyers with a quite delicate jizz and noticeably prone to resting on bare ground without nectaring. The main food plant is Ribwort Plantain.

Once fully warm they then perched mostly with wings closed, offering very pleasing underwing studies (above and below) of the white and orange banded patterning, interspersed with lines of black dots. By mid-morning as temperatures climbed to 25 deg C or more good numbers of Glanvilles became active all along the cutting and the number of observers also grew.

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A butterfly of open, grassy hillsides and cliffs, the Glanville Fritillary is distributed widely across most of mainland Europe but is on the extreme north-western edge of its range in the British Isles. Since the mid-19th century the species has been confined to cliffs on the southern coast of the Isle of Wight. Emergence typically begins in mid-May and peaks in early June before numbers decline quickly, so there is limited scope for observing them. Certainly the opportunity to do so at Hutchinson’s Bank remains very much appreciated by British wildlife enthusiasts whatever the controversy surrounding the colony’s “introduced” status.

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For new visitors to this blog who might have been directed via a Glanville fritillary web search, the different posts presented herein on British Butterflies are regularly referred to. The following may also be of interest:

Marsh Fritillary et al @ Battlesbury Hill, Wilts – 624 views

High Brown Fritillary @ Aish Tor & Heddon Valley, Devon – 436 views

Pearl-bordered Fritillary @ Rewell Wood, Sussex – 260 views

Pearl-bordered Fritillary in the New Forest, Hants – 208 views

Pearl-bordered Fritillary re-visit @ Rewell Wood, Sussex – 204 views

Marsh Fritillary @ Strawberry Banks, Glos – 199 views

Pearl & Small Pearl-bordered Fritillaries @ Wyre Forest, Worcs – 182 views

Small Pearl-bordered Fritillary @ Bentley Wood, Hants – 176 views

Also:

Duke of Burgundy at Noar and Butser Hills Sussex – 214 views

Scotch Argus @ Smardale Gill, Cumbria – 180 views

Large Blue @ Daneway Banks, Glos – 177 views

Duke of Burgundy @ Incombe Hole, Bucks – 96 views