Moths Counted

In 2006 Butterfly Conservation started the Moths Count project working with a wide ranging partnership of funders, organisation and individuals. The project aimed to set up a National Moth Recording Scheme (NMRS) and to bring together the information generated by moth-ers across the country into a single national (UK, Isle and Man and Channel Islands) database.

A major milestone in this project was the publication in 2011 (the copyright notice indicates it was finalised in 2010) of The Provisional Atlas of the UK's Larger Moths. The atlas contains, for the first time ever, national distribution maps for the Geometridae and the first national maps for over 30 years for most of the other species. Given the change in distribution of Britain's moths species over that period (see for instance Butterfly Conservation's 2006 publication The State of Britain's Larger Moths), this is an important publication.

Having seen a near final draft of this at the 2010 BENHS exhibition, I'd been eagerly waiting for the Atlas's publication since the end of last year so quickly rushed in my order as soon as the announcement was made. I was not alone in this: I understand that demand was in excess of that anticipated and that the entire print run was sold out within a few weeks. More have now been printed.

The Atlas opens with brief summary of the Moths Count project and then moves in to describe the data set. The maps in the Atlas are based on the 11.3 million records held in the NMRS as at the end of July 2010. Current historical records have been included, but the bias is towards modern records, and inclusion of historical record data is patchy nationally. Coverage (at a 10km-square level) seems good, with records from the vast majority of records from the region. Maps illustrating those areas without records, or where few species have been recorded, provide a good guide to where future recording effort could be targeted.

Following brief sections explaining the approach taken in the Atlas and providing caveats for users of the data, the main body of the book, 434 pages out of 454, consists of distribution maps presented two to an A4 page. The distributions maps show moth records at a 10km-square resolution with records before 2000 illustrated with a hollow circle and those from 2000 onwards with a black circle. The choice of 2000 as an old/new split is perhaps arbitrary, but any other date would be equally arbitrary. Data quality has been maintained by ensuring that all records in the NMRS (and hence this Atlas) have been submitted through county moth recorders (all expert volunteers). This is important to ensure accuracy, particularly for some of the more difficult-to-identify species.

Not every macro-moth species recorded is included, but the only omissions are of species deemed to have occurred only occasionally and solely through accidental importation. Very scarce natural migrants have been mapped.

On the whole the presentation of the maps is extremely clear, with only occasional difficulty coming from scarce species with historic coastal records where the few white circles can be difficult to spot (for instance, if you did not already know where Dusky Clearwing Paranthrene tabaniformis had been found, it could take a bit of time to spot it on the maps).

Like, I suspect, many people one getting my copy I turned to the pages with interesting species I have recorded to see what their distribution looks like. So it was nice to see the clear cluster around my area (London) of Tree-Lichen Beauty Cryphia algae, a species I was really pleased to take at light for the first time in 2006 (and every year subsequently).

For a few species, additional maps showing 'aggregates' of difficult-to-split species are included, such as Copper/Svensson's Copper Underwing Amphipyra pyramidea/berbera. Hopefully the publication of British and Irish moths: an illustrated guide to selected difficult species, also from Butterfly Conservation and the NMRS, will help even more moth-ers in the future to identify these down to species level.

From its subtitle "covering the use of genitalia characteristics and other features", it is clear that this is a book for those looking to take their mothing a bit further, but with learning the mysteries of 'gen det' on my 'to do' list for this year this was another I was keen to own.

A helpful section explains the techniques necessary to start dissection of moths, a handy glossary is provided to help you tell your ampulla from your endophallus, and then it is into species accounts. These consist of text discussion of external diagnostic features and a description of the diagnostic morphological characteristics of the male and female genitalia (sometimes presented in the form of a key). High-quality pictures of genitalia preparations are included to illustrate these points. For some species — for example the Grey Pine Carpet/Spruce Carpet Thera obeliscata/britannica aggregate — photographs of the details of external morphological characters are also shown (in this case, details of the antennae).

Even for those who have no intention of ever dissecting a moth, this publication is worth having. The quality of information on external characteristics (and illustration) is better than that which can (given space constraints) be included in any of the popular field guides currently on the market, and used in conjunction with these I will find this a worthwhile publication to own, even if 'gen det' never moves from my 'to do' to 'done' list.

To take just one example, it is useful to have a description of all the features for the Copper Underwing aggregate, explaining the palp character often mentioned on discussion groups, and explaining the criticisms of it and why it is unreliable. It was, however, a bit more disturbing to discover that the underside of the hindwing character for this group, upon which I and many others rely, "is not totally reliable".