Cloudburst takes Its toll – but Clouded Yellows continue to shine

GH and BG walked transect 22 on the morning of 31st August. The weather was mild with a mixture of sun and cloud.
As we’d anticipated, the 30-minute torrential cloudburst of three days earlier had a dramatic and detrimental effect on the number of butterflies still flying: last week’s total of 199 plummeted to only 48 for this week. It was the Meadow Browns who were hit hardest, with a reduction from 108 last week down to only 13. Small Heaths were also reduced, down to 21 from last week’s 51. Once again, there was a single Brown Hairstreak in the oak trees bordering Hill Wood Field but this time he/she settled long enough to be photographed. 
​It is the sixth week in succession that we’ve recorded Clouded Yellows. This is remarkable because in previous years we’ve thought ourselves lucky to have seen a single CY, yet so far this season we’ve counted a mighty 46.

​Count details:
​21 Small Heath
13 Meadow Brown
4 Clouded Yellow
4 Small Copper
3 Brown Argus
1 Brown Hairstreak
1 Common Blue
1 Small White

​Count summary:
48 butterflies from 8 species.

The elusive late-summer butterfly

Brown Hairstreak - Brian Gardner

Brown Hairstreak (Thecla betulae)  

• Unlike most species, Brown Hairstreaks emerge in late July-September, making them one of the last butterflies to appear each year.
• Look up! Adults spend much of their time high in the tree canopy, particularly around ash, oak and other trees, so they can be surprisingly difficult to spot. Females are larger and have distinctive orange patches on the wings.
• A tiny time capsule: Females lay their eggs singly on young blackthorn twigs, where the eggs remain throughout the winter. The caterpillars hatch the following spring – before the leaves have fully developed.
• When to see them in the UK: Late July-September, with August often the best month. Warm, sunny weather gives the best chance of seeing adults, including around blackthorn-rich woodland edges and hedgerows like those that border Hill Wood Field.

If you would like to know more about any of the butterfly species mentioned, 
​visit ​butterfly-conservation.org

​This week's survey by Graham Harris and Brian Gardner submitted to 
​Butterfly Conservation (UKBMS).
​Report by GK, BG & AI. Header photo of Small Heath by Duncan Jennings.
Brown Hairstreak photo by Brian Gardner.