Numbers still high

21/7/2025

Once again, the heat was on – literally – as we braved sweltering temperatures and sticky humidity for our walk around the 12 sections of our transect in Chipstead Valley.
Fortunately, while we may have wilted a little, the butterflies positively thrived, with numbers remaining impressively high. As in recent weeks, Gatekeepers and Meadow Browns dominated the count, basking in the sun and jostling for top spot in the tally.
Purple Hairstreaks continued to hold their ground in Hill Wood Field, playing hide and seek among the oaks on the edge of the path.
A seasonal milestone came with the sighting of our first Chalkhill Blues of the year – a welcome return of this chalk downland specialist. And for added excitement, we recorded a solitary Small Blue near the end of Hither Field – perhaps an unexpected second brood individual, defying the calendar with its appearance.
With each walk, the butterfly season reveals more surprises – and with weather like this, the best may be yet to come.

Count details:
267 Gatekeeper
221 Meadow Brown
85 Common Blue
19 Purple Hairstreak
15 Silver-washed Fritillary
12 Speckled Wood
10 Small White
9 Small Heath
   8 Marbled White
   8 Large White
   8 Small Copper
   6 Small/Essex Skipper
   5 Ringlet
   4 Chalkhill Blue
   4 Comma
   3 Brimstone
   3 Brown Argus
   3 Holly Blue
   1 Dark Green Fritillary
   1 Red Admiral
   1 Small Blue
Count summary:
693 butterflies from 21 species.
For more info on these species visit
butterfly-conservation.org

Butterflies of the week

Chalkhill Blue (Polyommatus coridon) – a specialist of sunny slopes and chalky grasslands:

Males are a striking pale silvery-blue, while females are brown with orange spots – and both are superbly camouflaged on bare ground.
This species relies almost exclusively on one plant: Horseshoe Vetch (Hippocrepis comosa), which is the sole food source for its caterpillars, restricting its habitat in Chipstead Valley.
Males are often seen in large groups, patrolling warm, sheltered areas in search of females, sometimes forming impressive mating swarms.

A true icon of Britain’s chalk downlands, but sadly declining where its food plant habitat is lost.

Chalkhill Blue, Stagbury - Liz North

Brown Argus (Aricia agestis) – small, subtle, and easily mistaken, but full of surprises:

It may look like a female Common Blue, but the Brown Argus has no blue at all – check for its all-brown wings and twin orange borders.
Unlike many butterflies, it doesn’t need one specific host plant – caterpillars happily munch on various geranium species.
It can produce two or even three generations in a good summer, making it a surprisingly fast breeder for its size.