COLLEMBOLA > ENTOMOBRYOMORPHA > ENTOMOBRYOIDEA > Isotomidae > Isotominae

The Isotoma genus is represented in Britain by just four species, I.caerulea and I.riparia which have unclear status as there are so few records of either species, and I.anglicana and I.viridis that can be confused.

Isotoma viridis is regarded as being the most common and widespread, but even ignoring possible misidentification, there are only a very small number of accepted records. The problem is two-fold. Firstly, that identification can only be accurately determined by microscopic examination of the manubrial teeth and the dens, and secondly that an official record would have to be submitted and verified. Very few people are going to go through that process, which is why so many species are only recorded by a few individuals who specialise in them. That said, the identity of the individual featured here was confirmed on the FB 'UK Collembola' group even though, strictly speaking, it should be listed as Isotoma cf.viridis. They tend to be more greenish than the other species, but specimens can be very variable, ranging from dirty-yellow to reddish-brown, or almost black - probably darkening with age. The colour though is uniformly distributed over the body. Isotoma viridis can grow to a length of 4mm.

In the bottom left-hand corner of the second photo below there's one of the tiny yellow globular-bodied species - possibly Sminthurinus aureus. When you think that Isotoma viridis is barely 4mm long, it doesn't take much working out to see that the other species is under a 1mm, which helps to explain why they can often go unseen.