39.001 Blastodacna hellerella (Hawthorn Cosmet)
ws: 10-11mm; May-Aug; hawthorn (Crataegus monogyna), midland hawthorn (Crataegus laevigata); common throughout Britain, except N.Scotland
Blastodacna hellerella §1 male
ID: To date I have not been convinced of any means of distinguishing this species from B.atra. Said to be distinguished by B.hellerella having the white parts of the forewing pure white and B.atra having these areas creamy white with additional yellow-ochreous scales at the forewing base (MBGBI4.1). In comparison of web images these differences are wholly unconvincing. It is notable that UKMoths does not show any images of B.atra and on the B.hellerella page it shows a dark form from NW England that was "originally believed to be B.atra, but now thought to be dark forms of B.hellerella".
Male genitalia: Comparative images are shown at Moth Dissection and several dissections are shown of each species. On the comparative image the anellus lobes and aedeagal cornuti are arrowed (implying a difference). Another image of B.hellerella states "anellus arms narrowing distally to less than half width of base" and it is possible that this is a valid distinction (with the anellus lobe not narrowing so much in B.atra); but differences in the preparations shown don't seem to me to show any reliably consistent differences in the anellus lobes between the species. The comparative aedeagal images appear to show 2 cornutal bundles in B.hellerella and only one in B.atra - but the former is shown with the vesica everted and the latter not, so this is also not a convincing distinction.
Male genitalia: Comparative images are shown at Moth Dissection and several dissections are shown of each species. On the comparative image the anellus lobes and aedeagal cornuti are arrowed (implying a difference). Another image of B.hellerella states "anellus arms narrowing distally to less than half width of base" and it is possible that this is a valid distinction (with the anellus lobe not narrowing so much in B.atra); but differences in the preparations shown don't seem to me to show any reliably consistent differences in the anellus lobes between the species. The comparative aedeagal images appear to show 2 cornutal bundles in B.hellerella and only one in B.atra - but the former is shown with the vesica everted and the latter not, so this is also not a convincing distinction.
Dissection
Male genitalia
Female genitalia
§1 Foulness, Essex; 29/06/2008; male; fw 4.7mm
§2 Westcliff-on-sea, Essex; 02/07/2008; male; fw 5.3mm
§3 Westcliff-on-sea, Essex; 09/07/2010; fw 5.7mm
§4 Westcliff-on-sea, Essex; 14/06/2011; male; fw 5.1mm
§5 Strumpshaw Fen, Norfolk; 07/07/2013; female
§6 Arne, Dorset; 06/07/2016; male; fw 5.2mm; to light
§7 Romansleigh, Devon; 25/06/2016; male; fw 5.4mm; to light
All images © Chris Lewis
§2 Westcliff-on-sea, Essex; 02/07/2008; male; fw 5.3mm
§3 Westcliff-on-sea, Essex; 09/07/2010; fw 5.7mm
§4 Westcliff-on-sea, Essex; 14/06/2011; male; fw 5.1mm
§5 Strumpshaw Fen, Norfolk; 07/07/2013; female
§6 Arne, Dorset; 06/07/2016; male; fw 5.2mm; to light
§7 Romansleigh, Devon; 25/06/2016; male; fw 5.4mm; to light
All images © Chris Lewis
Page published 2011 (§1-4) | §5 added 09/04/2013 | §6 and ID text added11/09/2016 | §7 added 07/01/2017
