73.037 Acronicta (Triaena) tridens (Dark Dagger)
fw: 17-20mm; May-Jul, occasionally bivoltine Sep-Oct; various broadleaved trees and shrubs; common in S.England and S.Wales, local further north.
ID: Indistinguishable on external features from A.psi (Grey Dagger). Forewing ground colour ranges from pale to mid-grey; clear black markings include a long branched basal streak, a streak to the tornus, edging between oval and kidney marks.
Male genitalia: In A.tridens apex of the sacculus is produced into a point while in A.psi it is blunt. In both species there are two subapical teeth; in A.tridens the produced apex makes a third tooth (‘tridens’ = ‘three teeth’).
Female genitalia: A.tridens has an appendix at the junction of the ductus bursae with the corpus bursae; this appendix is smaller in A.psi.
See A.tridens vs A.psi for further information.
Male genitalia: In A.tridens apex of the sacculus is produced into a point while in A.psi it is blunt. In both species there are two subapical teeth; in A.tridens the produced apex makes a third tooth (‘tridens’ = ‘three teeth’).
Female genitalia: A.tridens has an appendix at the junction of the ductus bursae with the corpus bursae; this appendix is smaller in A.psi.
See A.tridens vs A.psi for further information.
§1 Foulness, Essex; 11/07/2010; male; fw 18.0mm
§2 Newgale, Pembrokeshire; 20/05/2011; female
§3 Strumpshaw Fen, Norfolk; 10/07/2015; male; fw 16.8mm; to light
§4 Foulden Common, Norfolk; 29/06/2017; female; fw 18.9mm; to light
§5 Foulness, Essex; 24/06/2017; female; fw 17.3mm; to light
§6 Leworthy, Devon; 26/07/2021; male; fw 16.8mm; to light
§7 Leworthy, Devon; 27/07/2021; female; fw 18.4mm; to light
All images © Chris Lewis
§2 Newgale, Pembrokeshire; 20/05/2011; female
§3 Strumpshaw Fen, Norfolk; 10/07/2015; male; fw 16.8mm; to light
§4 Foulden Common, Norfolk; 29/06/2017; female; fw 18.9mm; to light
§5 Foulness, Essex; 24/06/2017; female; fw 17.3mm; to light
§6 Leworthy, Devon; 26/07/2021; male; fw 16.8mm; to light
§7 Leworthy, Devon; 27/07/2021; female; fw 18.4mm; to light
All images © Chris Lewis
Page published 03/04/2015 (§1-2) | §3 added 30/12/2015 | §4 added 05/10/2017 | §5 added 22/10/2017 | §6&7 added 20/08/2021