Following a suggestion at the Monmouthshire Moth and Butterfly Group AGM in March, I have analysed the Gwent record sets in terms of 1km by 1km (1km2) squares. There are 1628 1km2 squares falling wholly or partly within Gwent. The highest species total for a single square is 456 macrolepidoptera (butterflies plus macromoths), but there are 425 squares (26% of the total) with no butterfly or macromoth records at all.
There is always a reason why particular squares are under-recorded: uninteresting habitat, limited public access, difficult terrain for access, only a very small portion of the square lying within Gwent etc. Distribution maps are usually plotted on a 2km2 (four 1km2 squares) or 10km2 (one hundred 1km2 squares) basis, where a record is required for only one 1km2 square in each case for a “dot” to appear on the map. Hence distribution maps can suggest species are more widely distributed than they actually are.
The complete analysis is set out in the document linked below. Hopefully people will be able to start recording in some of the "zero squares" to help fill in the gaps.
1km x 1km squares