Learning to Triple-Check Myself

Don't ya just love starting out on a new platform by making a great big mistake?
To be sure I have been on iNaturalist for a little while now, and been referencing it for several years, but for one of my first big identification projects I decided to tackle all the observations of millipedes in Southern California, where I am based. I say all, really I mean all the polydesmidan and spirobolidean observations as the julids, parajulids, cambalids, and other more obscure groups I am not so familiar with. Anyway, the majority of observations are, of course, of the widespread invasive species Oxidus gracilis. Some time ago myself and a friend had compared O. gracilis and Asiomorpha coarctata, as the two are very similar looking and easy to mix up if careful attention is not paid, and made a guide to differentiating them. To shorten a long story, I had misunderstood the criterion for telling the two apart; to be sure, the most obvious external difference is that on the middle segments (8th and 9th segments) the paranota are flared posteriorly and extend past the segments themselves on A. coarctata, while on O. gracilis this sort of exaggerated flaring only starts in the last five segments or so. See a photo comparison here: http://cookislands.bishopmuseum.org/MM/MX5/5AT260_Asio_Oxid_RR1_GM1_MX.jpg.
BugGuide page for A. coarctata: https://bugguide.net/node/view/103087
BugGuide page for O. gracilis: https://bugguide.net/node/view/26414

However, I thought that the presence of flaring period meant that the specimen had to be A. coarctata. So after challenging 50+ observations of "O. gracilis" as actually A. coarctata, I began to get suspicious that there could be no Oxidus in Southern California at all. Further research revealed what I already noted above; flaring of the paranota is found on both species, just on O. gracilis it is largely absent until about the final 1/3rd of the specimen. Naturally this meant going back through all those observations and fixing the identifications on them, after which I contacted my friend, who unlike me had understood the difference, though since the subject had never really arisen again in our conversations (other than the both of us wondering how so many people could be wrong over this ID on iNat in our respective areas, ha ha) and our guide had already been a bit vaguely worded to start with my misunderstanding was never realized until now.
This is all after double-checking our original findings. Needless to say it was quite humbling for me to see how easy it is to be wrong, something I sometimes forget in the heat of the moment when I'm madly tearing through observations, and reminded me again of how important it is to triple-check your work.



Posted on January 09, 2022 08:25 AM by arthroverts arthroverts


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