73.334 Diarsia rubi (Small Square-spot)
fw: 12-16mm (Waring & Townsend), ws: 30-38mm (MBGBI9); bivoltine in England and Wales May-Jun, Aug-Sep, univoltine in Scotland Jun-Jul; various herbaceous plants and heather; common throughout GB.
Diarsia rubi (Small Square-spot) §2
ID: Forewing ground colour pale to dark pinkish-brown with variable banding and clouding with reddish-brown or dark brown. Similar to D.mendica (Ingrailed Clay) but D.rubi can usually be recognised from its smoother more evenly curved postmedian line; that of D.medica being more scalloped and irregularly curved. Distinguishing D.mendica/rubi may require genital examination and this is covered by the Difficult Species Guide.
The status of D.florida (Fen Square-spot) is uncertain. It is regarded as a separate species in the RES Checklist, but there are no diagnostic external characters, it has identical genitalia to D.rubi and hybridisation of the two forms produces fertile offspring. It is said to average larger, paler and brighter than D.rubi and has a single generation late June-July, between the two generations of D.rubi. It occurs in E.Anglia, N.England and Wales. Scottish populations of D.rubi/florida are univoltine Jun-Jul and are currently accepted as D.rubi, but may be better treated as D.florida.
The status of D.florida (Fen Square-spot) is uncertain. It is regarded as a separate species in the RES Checklist, but there are no diagnostic external characters, it has identical genitalia to D.rubi and hybridisation of the two forms produces fertile offspring. It is said to average larger, paler and brighter than D.rubi and has a single generation late June-July, between the two generations of D.rubi. It occurs in E.Anglia, N.England and Wales. Scottish populations of D.rubi/florida are univoltine Jun-Jul and are currently accepted as D.rubi, but may be better treated as D.florida.
Male genitalia: In D.medica the uncus is evenly narrow throughout its length; the valva is broad of roughly even width to 2/3 then narrowing somewhat to the cucullus (valva width ~ 2x cucullus width); the sclerotisation on the inner (ventral) face of the valva has 3 processes - the most costal of these (the ampulla) is narrow and twisted, the central process is flattened, the most ventral process (the harpe) is narrow and straight; the juxta is narrow and pointed. In D.rubi the uncus expands from base to near its apex which is rounded with a small central point; the valva expands centrally and narrows sharply to the cucullus (valva width ~3x cucullus width); the sclerotisation on inner face of valva has two processes - both the ampulla and harpe are longer than in D.mendica and the harpe is broad with an angulate costal edge and a curved ventral edge; the juxta is broad with an emarginate apex.
Female genitalia: In both D.mendica and D.rubi the ostium is broad with sclerotised anterior and lateral margins. In D.mendica the lateral margins are broad; in D.rubi the lateral margins are narrow.
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§1 Westcliff-on-sea, Essex; 31/08/2007; fw 15.2mm
§2 Foulness, Essex; 23/05/2009 §3 Westcliff-on-sea, Essex; 15/08/2009; fw 15.2mm §4 Foulness, Essex; 22/08/2009; male; fw 13.9mm §5 Moved to D.florida §6 Moved to D.florida §7 Newgale, Pembrokeshire; 14/05/2011; male; fw 16.8mm §8 Newgale, Pembrokeshire; 15/05/2011 §9 Lands End, Cornwall; 06/06/2013 §10 Strumpshaw Fen; 10/05/2014; male §11 Compton Bishop, Somerset; 27/08/2014; male §12 Compton Bishop, Somerset; 27/08/2014; male; fw 15.0mm §13 Foulness, Essex; 11/06/2016; male; fw 15.3mm §14 Foulness, Essex; 13/08/2022 All images © Chris Lewis |
Scottish specimens
§1 Bridge of Awe, Argyll; 24/06/2011; fw 17.0mm §2 Kinlochleven, Argyll; 03/07/2011; male; fw 16.8mm §3 Kishorn, Ross & Cromarty; 22/06/2022 |
Page published 04/02/2017 (§1-12 and Scot §1-2) | §13 added 10/05/2017 | Scot §3 added 11/12/2022 | §14 added 23/12/2022 |
§5&6 moved to D.florida 27/03/2024
§5&6 moved to D.florida 27/03/2024
