291 form favicolor (Mathew's Wainscot)

73.291 Mythimna (Mythimna) pallens form favicolor (Mathew's Wainscot)

ws: 34-42mm (MBGBI9.1), fw: 16-18mm (Waring & Townsend); Jun-Jul, occasionally bivoltine Sep; common saltmarsh grass (Puccinellia maritima); NS-B in saltmarsh on S&E coasts of England.
Synonym: Mythimna (Mythimna) favicolor
Formerly considered to be a separate species, now considered as a saltmarsh variant of M. pallens (Common Wainscot)

Mythimna (Mythimna) favicolor (Mathew's Wainscot) §1 male

ID: Form favicolor averages slightly larger then f.pallens but most specimens will be in the overlap range. There does not seem to be an absolutely reliable means of distinguishing them, but, in addition to a saltmarsh habitat, the following may help: 1) Forewing ground colour - usually sandy-orange or straw in favicolor, usually pale straw or reddish-brown in pallens; 2) Veins - are not pale-marked or are indistinctly pale-marked in favicolor, usually distinctly pale-marked in pallens; 3) Postmedian line of dots - this is quite variable in both species but is usually represented by at least 2 dots in favicolor, whilst it is not infrequently absent in pallens; 4) Hindwing upperside - said to be usually off-white with grey streaks in favicolor, white with a variable grey suffusion in pallens (but I think pallens is so variable with respect to this feature that it cannot be used as an aide to identifying favicolor. There are no genital differences between favicolor and pallens.

Variation
Dissection
Male genitalia
Female genitalia

§1 Foulness, Essex; 28/06/2008; male; fw 18.2mm
§2 Foulness, Essex; 03/07/2010; female; fw 17.6mm
§3 Foulness, Essex; 27/06/2015; female; fw 16.3mm
§4 Foulness, Essex; 27/06/2015; male; fw 16.2mm
§5 Foulness, Essex; 03/08/2018; male; fw 13.8mm!
§6 Foulness, Essex; 08/07/2023
All images © Chris Lewis

Page published 27/12/2016 (§1-4) | §5 added 18/02/2019 | downgraded from species status Jun 2022 | §6 added 19/12/2023