73.038 Acronicta (Triaena) psi (Grey Dagger)
fw: 17-20mm; May-Aug, occasionally
bivoltine Sep-Oct; various broadleaved trees and shrubs; common throughout GB.
Acronicta psi (Grey Dagger) §3 male
ID: Indistinguishable on external features from A.tridens (Dark 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; according to the Difficult Species Guide, 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; according to the Difficult Species Guide, this appendix is smaller in A.psi.
See A.tridens vs A.psi for further information.
§1 Westcliff-on-sea, Essex; 18/07/2007; male
§2 Westcliff-on-sea, Essex; 03/06/2010; male
§3 Cyffdy Farm, Gwynedd; 22/06/2010; male; fw 19.7mm
§4 Mull; 05/07/2011; female; fw 18.8mm
§5 New Forest, Hampshire; 05/06/2012; male
§6 Snettisham, Norfolk; 06/07/2013; male
§7 Buttermere, Cumbria; 21/06/2014; female; fw 19.8mm
§8 Mull; 21/06/2018; male; fw 19.7mm
§9 Stour Wood, Essex; 06/06/2021; female; fw 19.1mm
All images © Chris Lewis
§2 Westcliff-on-sea, Essex; 03/06/2010; male
§3 Cyffdy Farm, Gwynedd; 22/06/2010; male; fw 19.7mm
§4 Mull; 05/07/2011; female; fw 18.8mm
§5 New Forest, Hampshire; 05/06/2012; male
§6 Snettisham, Norfolk; 06/07/2013; male
§7 Buttermere, Cumbria; 21/06/2014; female; fw 19.8mm
§8 Mull; 21/06/2018; male; fw 19.7mm
§9 Stour Wood, Essex; 06/06/2021; female; fw 19.1mm
All images © Chris Lewis
Page published 03/04/2015 (§1-7) | §8 added 21/04/2019 | §9 added 15/11/2021
