When you can't ID that bumble bee quite to species...

Many species of bumble bee (Bombus) mimic each other and are difficult or impossible to tell apart from photos. For example, B. vosnesenskii and B. caliginosus males are distinguished by a subtle difference in antennal proportions. To tell apart females of these species, you either need a good view of the underside of their abdomen or a good view and expert knowledge of their face shape. This mimicry means that many Bombus observations can’t be ID’d past subgenus level with even quite good photos. However, there are over 30 species in just the subgenus Pyrobombus, and sometimes it is possible to narrow it down to just two or a few among these. iNaturalist doesn’t allow multi-species categories like this in the official taxonomy for IDing because they are not monophyletic. We value this information, however, so we decided to set up a new observation field to allow us to capture it for bees in the subgenus Pyrobombus.

To use this observation field, first go to an iNat observation. Scroll down, looking at the categories in the right sidebar, until you find “Observation fields.” There, you click in the “Choose a field” text box and type in “Pyrobombus” (but without the quotation marks). Then a new list pops up, at first showing its first entry, “IDable-to-species.” Click on that and you’ll see a list of common sets of species that can’t always be distinguished from photos. Once you’ve clicked on the group you want, click “Add” to save the entry. Here is an example of an observation where this field has been used.

We hope that if this field is used widely enough, its easily-exportable data will give valuable range information. We also hope it will reduce the temptation to go all the way to species when it isn’t quite justified by photos. Let us know if you like it! We can add other fields for other subgenera if people find it useful.

We owe thanks to BugGuide, from whose taxonomy we got the lists of difficult-to-distinguish species. We are also grateful to @keirmorse, who suggested this way of using observation fields in response to our question on the iNat forum.

Posted on 28 de abril de 2021, 04:09 AM by eebee