josscarr's Journal
One of the few UK Onychiruoidea springtails that can be distinguished from shape alone is Kalaphorura burmeisteri. To quote Matthew Shepherd (a UK Soil Ecologist): "this is one species that can be identified by shape alone. It's the only white, blind, springless podger that his this tapering shape, fattest around the middle. Often compared to the Michelin man!"
Original source (including photos): https://www.facebook.com/groups/438740999565613/permalink/3185136071592745/
As far as I am currently aware, there is no reliable way to generally distinguish UK springtails from the families Onychiuridae and Tullbergiidae (together superfamily Onychiuroidea) from UK springtails in the family Hypogastruridae, based on standard field photographs alone (i.e. not macro-photography or microscopy). That is not to say there there aren't at least a few species within these families which are distinctive enough to ID to species from photographs (e.g. Kalaphorura burmesiteri, see https://tinyurl.com/uh3fmb), but just that the general distinction between families can generally not be made.
This assertion is in contradiction to Dallimore and Shaw's (2013) 'Illustrated key to the families of British Springtails (Collembola)', which argues that the distinction can be made (presuming Neanuridae, Odontellidae and Poduridae have all been eliminated as options) based on the pigmentation of the specimen. It is argued that all Hypogastruridae are pigmented whereas all Onychiuroidea are not.
In reality, however, this appears not to be the case. There are several unpigmented Hypogastruridae, some of which closely resemble Onychiuroidea. Of those for which there are photos listed on the global Springtail database (https://www.collembola.org/), there are at least 5 species of unpigmented Hypogastruridae:
Of these, Mesogastrura libyca in particular looks very similar to some Onychiuroidea. It should also be explicated that many species lack photographs on the database and so could also easily also be unpigmented and similar in appearance to some Onychiuroidea.
I therefore urge that caution should be taken when distinguishing Hypogastruridae from Onychiuroidea on the basis of pigmentation, and that in most cases observations should be left at order unless other determinant characters (e.g. those assessable through microscopy or good quality macrophotography) are visible.
As far as I am currently aware, the two Poduromorpha springtail families Neanuridae and Hypogastruridae cannot easily be distinguished from one another based on field photography alone. Rather, details only visible through microscopic analysis are needed.
It is notable that this assertion differs with that made by Dallimore and Shaw's (2013) 'Illustrated key to the families of British Springtails (Collembola). According to that key, the distinction can be made based on the distinctiveness of the head from the thorax. In Neanuridae, it is argued, the head is indistinct, whereas in the other UK Poduromorpha families (Odontellidae, Poduridae, Onychiuridae, Tullbergiidae and Hypogastruridae), the head is notably distinct.
I am inclined to disagree with Dallimore and Shaw's key here because the 'distinctiveness' of the head from the thorax varies considerably along a gradient from 'clearly distinct' to 'clearly indistinct' – it is not a clear-cut matter. Furthermore, not only does distinctiveness appear to differ from species to species within the two families, it is also likely that distinctiveness can vary between individuals within a species (i.e. intra-specific morphological variation), and even over time for a single individual (based on environmental conditions, whether the springtail is feeding, resting, etc.).
See discussion on these observations for original thoughts:
According to Steve Hopkin (a UK Collembola expert) on his website (https://tinyurl.com/344w6nh4), 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 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 (https://tinyurl.com/344w6nh4), 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 distinguished from one another by the state of the first thoracic segment. Both Poduromorpha and Entomobryomorpha technically have three thoracic segments, however in Entomobryomorpha the first thoracic segment is greatly reduced dorsally, such that it almost appears as if the springtail has a 'neck'. Poduromorpha, in contrast, have a visible first thoracic segment. For a clear example, compare https://www.inaturalist.org/observations/75409414 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: https://inaturalist.org/observations/127831994) 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 on the global databse (https://www.collembola.org/), I strongly suggest that using this congregating feature as a determinant for an ID is inappropriate.
