This may be a fool's errand, but a comment on this post has inspired me to try to write a series of posts on how I identify adult moths. This will be based mostly on experience from Europe and Australia (and to a lesser extent New Zealand and North America) but I think much of it should apply to naturalists in most parts of the world. I'll add thoughts as I have time. Dealing with other life stages is harder but I may add some comments on that later.
This series currently includes the following posts:
In general moths are one of the easiest insect groups to identify. They can be attracted by light and easily photographed or captured for study. Wing patterns and other features are often obvious and distinctive enough to lead to species-level identifications or at least to a small number of related or confusion species.
Most of my own identifications are made on live moths or on photographs I have taken of live moths. This certainly means that I have many records for which I have no ability to get the necessary information (hindwings, underwings, genitalia, leg spurs, etc.) to reach a species-level identification. However it does also mean that it is possible to get an understanding of the lepidopteran biodiversity in a location rather quickly.
I usually set about identifying an unrecognised moth in the following way:
1) Assess likely groups
Based on resemblance to other moths, determine which taxonomic group or groups seem most likely (depending on familiarity, these groups may be superfamilies, families, subfamilies, tribes or genera).
2) Review moths from the region
For these groups, scan examples of the appearance of moths in these groups from the region in question (using images and descriptions in literature or web resources or using specimens in a collection). Access to better identification resources allows the ultimate identification to be more precise.
3) Evaluate possible matches
If a potential match is found, check for further information (other images, distribution, flight seasons, etc.) to determine plausibility.
4) Check relatives
If the match seems good and there are resources which list species known from the region, check close relatives (typically same genus) to see whether these are equally or more likely. This will determine how precisely it is safe to identify the moth.
5) If necessary, expand search
If nothing matches, return to 1) above and reconsider whether other taxonomic groups may be relevant.
This process becomes more and more efficient with increasing familiarity with the fauna from the region. Over time, familiarity is gained with the range of moths found in a region and most new individuals can be assigned to the most probable family, subfamily or genus using overall appearance and resemblance to other species. Getting to this level of familiarity involves using three tools:
Personal communication with knowledgeable naturalists, particularly in the field, but even contacts only known through email are highly useful.
Good, well-illustrated literature, in particular field guides that show moths in live positions. Most illustrated literature used photographs, although good paintings may make comparison easier.
Web resources, particularly those that provide easy ways to scan through illustrations of the range of species in a particular taxon from a given region. Such comparison with large numbers of species is usually easiest if the images are of pinned specimens - making the mental adjustment to map the patterns on a live species onto a spread specimen only takes a little practice.
I have created a post reviewing the literature and web resources I have found most useful for identifying moths, particularly in in Europe, Australia and North America.
Subsequent posts will explore how this applies with real moths.
Comments
excellent stuff, Donald. Many thanks for your efforts.
Thanks, Roger. I'll be interested in your comments on the next few posts as I try to give some triage directions for unknown moths.
It's also important to stress to people coming in to moth recording and identification that not all species are named (scientific name) yet, so it is entirely possible to find species that can't be placed to species (or even genus) on occasion, especially tropical species. Awareness that there are many groups of cryptic species should also be emphasized, and in these cases it is not possible to identify from photos only.....
Good point - I emphasise that particularly in relation to Australia in the second post, but I'll work that in as a more major theme. The most critical skill of all in something like iNaturalist is the ability to decide how precise an identification can safely be made for any particular organism given the current state of taxonomic revision and the availability of accessible resources and the information available from a photograph for that particular group and region.
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