Isotoma riparia?

First and foremost note the question mark!

This post is as much a point of interest as it is a pin to stop me trying to squirm out of a commitment to an identification. Here’s an admission for you. I have trouble with Isotoma and Isotomurus. The difference should be obvious! Alan Cann has shared a helpful crib on separating the two genus on his own website. Peter Shaw regularly reminds me of the difference in the mucro between the two (and stresses the need to look really, really hard for tricobothria!).

Still i don’t trust myself. In the image i have what i think to be Isotoma riparia (more fool me). They immediately threw me as they were a striking green much as i often see on Isotoma viridis . The features appeared then to be consistent and i keyed the species…

If i am honest i still don’t believe myself. I shall check again (and look for those trichobothria really, really hard) and if i still key here then Peter can pass the ultimate judgement!

Should it be confirmed this would be a genuinely interesting record of a species that is already said to be scarce and restricted.

Special thank you to Steve McWilliam and Susan Marley for collecting the specimens! Record details (Moore Nature Reserve, Lapwing Lane, Moore, Warrington, 07/03/2018, SJ57658584)


  1. They’re not easy to tell apart and I find trichinosis very hit and miss.

    1. I have some luck when checking for the ‘socket’ but am never quick sure if i am looking at the position of the trichobothria or something else, like a sensory organ. A lack of experience!

  2. Can these mites infest humans? I think they are attracted to people if they have a fungal infection!

    1. Hi Tracey, these are not mites but Collembola which are pretty much in a group to themselves! They do not infest people in any way despite a handful of internet myths that have no basis in the behaviour or ecology of these animals. They are harmless omnivores that largely live in the soil and form an important part of the soil ecosystem.

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