According to Steve Hopkin (a UK Collembola expert) on his website, there are 23 species of 'littoral' (meaning intertidal/seashore) springtails found in the UK. These 23 springtails are split across two orders (Poduromorpha and Entomobryomorpha) and five families (Hypogastruridae, Neanuridae and Onychiuridae within Poduromorpha; Entomobryidae and Isotomidae within Entomobryomorpha).
As far as I can tell, in most cases it seems to be very difficult if not impossible to ID any of these 23 springtails down to species from photographs and/or a description of habitat or behaviour alone. Rather, as per Steve Hopkin's website, it is only with a view of microscopic features that identifications can be made. That being said, one can certainly go down to order or family in some cases, particularly if close-up photos of individuals are provided.
Identifying to order:
According to Dallimore and Shaw's (2013) 'Illustrated key to the families of British Springtails (Collembola)', Poduromorpha and Entomobryomorpha can be easily distinguished from one another by examining the first thoracic segment. Both Poduromorpha and Entomobryomorpha technically have three thoracic segments. In Entomobryomorpha, however, the first thoracic segment of the three is greatly reduced dorsally, such that it almost appears as if the springtail has a 'neck'. Poduromorpha, in contrast, have a clearly visible first thoracic segment. For an obvious example of the difference, compare https://www.inaturalist.org/observations/221987468 with https://www.inaturalist.org/observations/194018768.
Identifying to family:
Within Poduromorpha (12 littoral species):
Within Entomobryomorpha (11 littoral species):
Congregating behaviour:
I am yet to see any definitive evidence that the 'congregating' behaviour exhibited by some littoral springtails (e.g. see here) is a unique feature of a distinct subset of the 23 littoral species. Given that many of the 23 littoral species lack everything besides a basic description, and some do not even have photos in the global database, I strongly suggest that using this congregating feature as any sort of determinant for an ID is inappropriate.
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Fixing some of the taxonomy in Poduromorpha now and filling the empty gallery images, I agree regarding congregation fwiw.
This seems to be evident in inland species as well as littoral ones and definitely not just A.maritima.
Would make a good project to pull together these observations!
We could at least annotate them with an observation field so they are easy to find down the line.
Which ones lack photos?
Some of these are on BOLD at least :
T.debilis - https://v3.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxid=360894
P.macfadyeni - https://v3.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxon=Protaphorura+macfadyeni&searchTax=
The ones for which I couldn't find photos on collembola.org are:
Xenylla humicola
Anurida denisi
Anurida thalassophila
Anuridella immsiana
Anuridella marina
Anuridella submarina
Thalassaphorura halophila
Pseudosinella halophila
Pseudosinella petterseni
Archisotoma besselsi
Archisotoma megalops
Archisotoma pulchella
Archisotoma theae
Halisotoma poseidonis
The BOLD photos tend to not be great for informing ID based on photographs in my experience given they tend to show specimens through microscopes and therefore with weird unnatural lighting setups.
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