This moth spent most of the afternoon sitting on the frame of the front door at home. I could not see it in our (admittedly rather compact) moth book, so posted it on iSpot. This yielded the suggestion, with several agreements, that it is a Riband Wave moth, to be precise, Riband Wave (non-banded form), Idaea aversata ab. remutata.
iSpot links to a map on the National Biodiversity Network. The map suggests that this particular moth is rather rare, or at least, not very often sighted or reported. iSpot also links to the Encyclopedia of Life, which contains images but no description. Had we found something rare in Sheffield?
So I Googled it, and found this page on the UK Moths site. It also shows a map, from NBN, which gives a whole different picture.
Why is this?
Well, one reason is that the map on UK Moths shows both forms of Idaea aversata. So, I went back to NBN and found the map for Idaea aversata, which presumably does not include ab. remutata. More coloured squares than before, but still not as many as the UK Moths map.
The reason? Following links from both maps reveals the datasets used. Click Datasets acknowledgements on the UK Moths map, and you see that the data comes from Butterfly Conservation - Macro moth provisional distribution. Scroll down on the NBN map and you see a long list of datasets that are included in their map. Keep going and you see further relevant datasets that there is no access to, and there it is, the Butterfly Conservation Macro moth provisional distribution.
So, possibly not so rare, and not the first sighting in Sheffield! What have I learned from this? One - always check the data sources that go into a map. Two - you may need to look in more than one place to get all the data.