74.0093 Nycteola degenerana (Sallow Nycteoline)
ws: 23-28mm (Wikipedia); bivoltine Jun-Jul, Sep-May; sallows (Salix spp), oak (Quercus robur); first British record W.York Sep 2022
Nycteola degenerana (Sallow Nycteoline) §1 female
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ID: At the time of writing I have not seen a description of this species other than the brief one at Wikipedia which states that it is the largest of the genus. With a fw of 12.1mm this specimen is larger than any N.revayana I have measured (range 10.1-11.8mm for 8 specimens).
Based on comparison of web images I offer the following: Similar to banded forms of N.revayana. Median fascia somewhat variable in breadth and strength, but always bordered by bold white antemedian and postmedian lines; in N.revayana these lines are seldom white. Curve at base of costa noticeably shallower in N.degenerana than in N.revayana. 
Line drawings of shape of base of costa from the forewings shown left
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Refs: Noctuoidea europaea (NE), Dufay, Dave Grundy (DG) by personal correspondence
Male genitalia:
Aedeagus – broader / more robust in degenerana (NE but not Dufay)
Cornutus - broader / more robust in degenerana (NE & Dufay)
In both species the costal margin of the valva has a projecting process at ~2/3 and an apical valvula (or cucullus). In revayana there is a substantial cluster of setae on the costal margin between the process and the valvula; this cluster is much less prominent in degenerana. The setae are about as long as the costal process in revayana, much shorter in degenerana. The valvula in revayana is rounded, more angular in degenerana.
There is a difference in the shape of the apex of the saccular margin in the drawings but it is not clear whether this is real or an artefact of the difficulty in setting Nycteola valvae flat. (All valval features described from NE drawings, Dufays drawings not good enough to comment).
The saccus of revayana has a bulge at ~1/2; more parallel-sided in degenerana. (NE & Dufay)
The juxta of revayana tapers more abruptly towards its posterior half than in degenerana. (NE, but not so clear in Dufay)
DGs notation indicates that the uncus of revayana is the narrowest of any European species but the drawings suggest there is not much difference c/w degenerana.
The A8 dorsal plate has a pair of posteriorly directed processes. In revayana these processes are drawn about as long as the space between their bases. In degenerana the processes are clearly longer than the space between their bases. (Dufay, not drawn in NE)
However, my preps of the dorsal plate in revayana show the processes clearly longer than the space between their bases and so any real difference is not as stated above. There is also a difference in the pattern of sclerotisation of both the ventral and dorsal plate.
Male genitalia:
Aedeagus – broader / more robust in degenerana (NE but not Dufay)
Cornutus - broader / more robust in degenerana (NE & Dufay)
In both species the costal margin of the valva has a projecting process at ~2/3 and an apical valvula (or cucullus). In revayana there is a substantial cluster of setae on the costal margin between the process and the valvula; this cluster is much less prominent in degenerana. The setae are about as long as the costal process in revayana, much shorter in degenerana. The valvula in revayana is rounded, more angular in degenerana.
There is a difference in the shape of the apex of the saccular margin in the drawings but it is not clear whether this is real or an artefact of the difficulty in setting Nycteola valvae flat. (All valval features described from NE drawings, Dufays drawings not good enough to comment).
The saccus of revayana has a bulge at ~1/2; more parallel-sided in degenerana. (NE & Dufay)
The juxta of revayana tapers more abruptly towards its posterior half than in degenerana. (NE, but not so clear in Dufay)
DGs notation indicates that the uncus of revayana is the narrowest of any European species but the drawings suggest there is not much difference c/w degenerana.
The A8 dorsal plate has a pair of posteriorly directed processes. In revayana these processes are drawn about as long as the space between their bases. In degenerana the processes are clearly longer than the space between their bases. (Dufay, not drawn in NE)
However, my preps of the dorsal plate in revayana show the processes clearly longer than the space between their bases and so any real difference is not as stated above. There is also a difference in the pattern of sclerotisation of both the ventral and dorsal plate.
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Female genitalia:
The ductus bursae of Nycteola species is largely represented by a broad antrum. In revayana the antrum is relatively small, and narrows posterior to the anterior ends of the anterior apophyses. In degenerana the antrum is large, extends anterior to the anterior ends of the anterior apophyses and narrows close to its junction with the corpus bursae. There is a patch of sclerotised spicules located at the anterior end of the antrum. In revayana this patch is distinctly quadrangular and there is a separate area of sclerotisation in a diverticulum arising from the narrowed portion of the ductus bursae. In degenerana the patch is broader and more rounded and there is no separate patch. (NE & Dufay) |
A8 and antrum of N.revayana (§10) left and N.degenerana (§1) right
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St Mary's, Isles of Scilly; 18/10/2024; female; fw 12.1mm; 2nd British record
All images © Chris Lewis
All images © Chris Lewis
Page published 31/10/2024 (§1)
