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Frosted Green
Polyploca ridens (Fabricius, 1787)
Drepanidae: Thyatirinae
1660 / 65.015
Photo © Ben Sale,  Stevenage, Hertfordshire (08/04/19)

Similar Herts & Middlesex Species: None
Forewing: 15-17mm.
Flight: One generation. Apr-May.
Foodplant:   Pedunculate Oak. Sessile Oak and Turkey Oak.
Red List: Near Threatened (NT)
GB Status: Common
Former Status: Local
Verification Grade:  Adult: 1

General comments:
This dark moth is often mistaken for a cuculliine noctuid, though the early date would rule out members of that subfamily.

Hertfordshire Notes:
It is likely to be found wherever mature oaks grow, typically in woodland. A larva was beaten from English Oak at Oxhey Woods in 1938 (Eric Classey); young saplings apparently do not support the caterpillar. The adult moth is very variable. At Bushey, Barry Goater recorded that 100 per cent of the population was referable to the melanic ab. unicolor Cockayne, in which the whole wing surface is dark blackish green with darker veins and no other markings. This form is currently (2023) very common in the woods around Bishops Stortford, though it forms perhaps only 50 per cent of the catch with the lighter ab. fumosa Warnecke, in which the pattern shows through, also present. I have not personally seen any typical, non-melanic examples in Hertfordshire, though some may be unreported.

Middlesex Notes:
Local, but affecting the majority of the area of the county except for the south-east (the built up area of London-proper). The lack of map dots in the south-west is confidently predicted to be a consequence of under-recording.

Recorded in 26 (63%) of 41 10k Squares.
First Recorded in 1887.
Last Recorded in 2024.

Latest Records
Date#VC10k - General Area
30/04/2024120TL30 - Hoddesdon / Cheshunt
13/04/2024121TQ09 - Watford / Rickmansworth
12/04/2024221TQ09 - Watford / Rickmansworth
11/04/2024120TL30 - Hoddesdon / Cheshunt
10/04/2024121TQ09 - Watford / Rickmansworth
07/04/2024120TL11 - Harpenden / Wheathampstead
07/04/2024120TL30 - Hoddesdon / Cheshunt
05/04/2024220TQ09 - Watford / Rickmansworth
30/03/2024120TL30 - Hoddesdon / Cheshunt
29/03/2024120TL30 - Hoddesdon / Cheshunt
Further info: Polyploca ridens
 
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