Flavescent: ‘the most magnificent springtail’

Having lived within 15 minutes’ walk of Hedgecourt Nature Reserve for my entire life and visiting it on a weekly basis during the holidays, one would be forgiven for thinking that I would have a fairly good grasp of the fauna and flora living on the site. Furthermore, having focused a lot of my effort on springtails over the past few years, that fact might be especially true for these small denizens of leaf-litter, soil and tree trunks. And, trying not to sound excessively dramatic, the afternoon of July 10 was not unlike any other. That was, until I found the holy grail of south Surrey woodland sexpartite-antennal entomobryid collembology.

The genus Orchesella is distinguished from all other British Collembola (springtails) by having the antennae divided into six segments (usually), which are of differing lengths. They’re fairly large as springtails go, with the largest reaching over 5mm in length. They’re also distinctively patterned, making them among my favourite genera, although before this month, I’d only recorded the two common species: Orchesella villosa and O. cincta. Six other taxa have been previously recorded in the UK, however of those only O. alticola (a montane species) and O. flavescens have had confirmed records – with the others either unconfirmed or referring to colour variations of O. villosa.

The scarcity of Orchesella flavescens can be highlighted by the fact that there were no reliable records of this species anywhere in the country between the years of 1925 and 2009, when a population was discovered in north Sussex, near Gatwick. Since then, a few other populations have been discovered in southern England, including one in Surrey. Given the relative proximity and similarity of these sites to the woodland habitats around me, I knew I was in with a chance of running into this species, although I would have to be very lucky. The appeal of Orchesella flavescens is amplified by the description of the taxon by the eminent recorder H. Womersley in The apterygotan fauna of the south west of England, published in the Proceedings of the Bristol Naturalists Society in 1924:

This, in my opinion, the most magnificent spring-tail, was again taken in its previously recorded habitat amongst dog’s mercury at Flax Bourton Combe, Som., May 17th, 1924.

Hence, I think that you can imagine my joy upon discovering a juvenile in my sweep-net on the afternoon of the 10th! Unusually for a springtail, it is instantly recognisable in the field without any magnification. While O. cincta has the third abdominal segment completely dark-pigmented and O. villosa has intricate and discontinuous patches of dark pigment across its body, O. flavescens has the pigment arranged in neat longitudinal lines.

Orchesella flavescens

I must confess that the photo above is not of the specimen I found on the 10th. However, it is even more exciting, for during a repeat visit on the 22nd, two further examples of O. flavescens were discovered, including this one! Considering that I’d spent many years visiting Hedgecourt without a hint that O. flavescens might be present there, to find the species on two occasions within the space of a fortnight is remarkable.

Another point of interest about the above image is the form of the antennae. A curious fact about Orchesella is that the antennae are often asymmetric – and this specimen of O. flavescens is a clear example of that. The antenna on the left has six segments (the basal segment is very small) whilst the one on the right has five. This lack or shortening of segments can occasionally be seen in other species where the antennae have been damaged, but as for why it occurs more frequently in Orchesella is unbeknownst to me.

The takeaway from this fantastic record of a seemingly scarce and good-looking springtail is that it is very unlikely that O. flavescens disappeared from the UK for over 80 years between 1925 and 2009. The populations we are discovering at the moment have likely been in situ for many years, and there are undoubtedly more awaiting discovery. This exemplifies the importance of better recording coverage of this taxonomic group which is often ignored by many naturalists. O. flavescens is the perfect springtail for even the casual naturalist to be on the lookout for: a large, distinctive species with no microscope required!