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:

• Ceratophysella succinea
• Ceratophysella armata
• Schaefferia emucronata
• Xenylla grisea (juveniles)
• Mesogastrura libyca

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.

Posted on April 5, 2024 12:23 PM by josscarr