Mottled Orache Moth Scrobipalpa atriplicella

The majority of records of this species in Norfolk are from the Brecks but in recent years there have been a few elsewhere. Formerly given the vernacular name Goosefoot Groundling.

I re-examined this one recently in the light of the population explosion of the very similar Beet Moth Scrobipalpa ocellatella, concerned that I might have misidentified one of them as it wouldn't have been a species I would have expected then. At the time I found this one, Beet Moth had not been recorded in Norfolk and was thought to be restricted to the south coasts of Britain - though that changed dramatically within 2-3 years. For some reason I didn't set the genitalia of this moth so can't re-examine it directly. I did take some photos of the genitalia, but unfortunately none of them show the corpus bursae. The key in MOGBI separates atriplicella from ocellatella based on the transition from the ductus to corpus bursae - gradual on ocellatella (and other spp.) and abrupt on atriplicella (and other spp.). I would have used this key, so presume it did show a clearly defined spherical corpus bursae, but I cannot now confirm that from my photos. The photos do show a honeycomb pattern on segment 8, superficially similar to that found on ocellatella. This concerned me at first as according to the MOGBI key it should be "at best weak" on the ventral zone - so had I in fact messed up Norfolk's first ocellatella?

In the end I decided my original ID was correct. Judging from photos of genitalia on the Moth Dissection website and the diagrams in MOGBI there are two differences in the shape and pattern of segment 8. Firstly the inner sides slope up more gradually on atriplicella - they are much more angled with a flat anterior edge (between the base of the apophyses anterior and the centre) on ocellatella. Also the honeycomb patterning is most intense along this edge on atriplicella, whereas it is stronger in from the edge on ocellatella. The lobe-like bits between the two lateral sides of segment 8 - I assume these are the anterior end of the ventral zone - are rounded and more intensely patterned in ocellatella and longer and a little less intensely patterned in atriplicella.

female Mottled Orache Moth Scrobipalpa atriplicella showing genitalia including close ups of segment 8 (focussed on ventral zone and on ventrolateral zones) and signum, North Elmham Cathedral Meadows (Norfolk, UK), 25th May 2019