General comments:
Widespread and Common in Hertfordshire where it is increasing in both range and population strength, although strangely sparse in the south-west. Formerly extinct in Middlesex it is now spreading into that county from the north-east.

Hertfordshire Notes:
Foster (1937) has the Oak Eggar 'Reported from all districts' and in Plant (2008) I suggested that this was a pretty fair assessment of the present day status. However, it is now apparent that the moth was probably genuinely absent from the blank areas in the map and that it has colonised much of Hertfordshire in the past twenty years. Records fall into two categories - occasional females taken in light traps and, more frequently, day-flying males. Unlike the northern subspecies of this moth, which feeds on heather, our southern subspecies is supposed to feed on a variety of deciduous trees and shrubs; in the London Area these include Common Hawthorn, Bramble and Hazel. Consequently, there appears to be a behavioural difference, with the diurnal males avoiding open situations and instead apparently associating with edge habitats such as hedges and woodland margins.

Middlesex Notes:
Other than old records from Finchley and Mill Hill in 1902 and then Ickenham in 1968, all Middlesex records are from 2004 onwards and affect the north-east only, in Trent Park and surrounding areas. In Plant (2008) I suggested that under-recording was the reason for the blank maps, but it is clear that I was incorrect: Prior to about 2004 the Oak Eggar was absent from Middlesex and has colonised the county since then in the north-east only.

Recorded in 24 (59%) of 41 10k Squares. First Recorded in 1887. Last Recorded in 2024. Additional Stats

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