I finally had the time to watch the webinar and then look at the ID Summaries Demo, yesterday. The first species discussed in that webinar, Hippodamia convergens, struck me as one that I might add to my identification repertoire. I have some personal experience with observing this species and the distinct, converging lines on the pronotum was a clear morphological feature that I could see in observation photos, without having to slog through the more confusing (and less visible) characters in a published key. And there were a good number of observations still at Needs ID.
I began reviewing these observations (limiting myself to the USA and Canada) and adding my IDs where these lines were clearly present. Then I came across an observation where there was a discussion in the comments about the possibility of that being H. sinuata. Although the thumbnail photo for that species is quite different in the color and markings on its elytra, that species apparently also has wide variation in those markings. While it was decided in that particular observation that the geographic range for that variation excluded H. sinuata, it left me without being able to distinguish these two species when they both have the convergent lines. Looking more closely at the other North American species, this problem also exists with H. glacialis, which may also have those convergent lines.
The comments that were the input for this demo were discussing differences between H. convergens and various species of Coccinella. These differences may be true and useful. The comments apparently did not go far enough into distinguishing all of the other species of Hippodamia.
I’ll note that when comparing the observations of these species, H. convergens is much more common than the other two, by more than two orders of magnitude. Taking that into account, and also considering the cases where I’m confirming the ID of the top identifier of the species, it’s statistically unlikely I made any mistakes last night. On the other hand, these similarities may be contributing to false identifications for the more common species. Are there other visible morphological differences I can use to be sure of my IDs? I’m an amateur, trying to take this responsibility seriously.
These issues have already been raised, in the abstract, in this discussion. Take this personal experience as a real-life case study.