Shrinking Springtails

Earlier this week I came across a springtail that gave me pause for thought. Allacma fusca was the very first springtail ever described scientifically (De Geer, Act. Stockh. 1743. p.296). At up to 3.5mm long, this is the largest member of the Sminthuridae, and compared to the rest of this family, quite distinctive. Normally, this species is unmistakable, but I hesitated over this specimen. There are two reasons for this. The first is simply that I have been shamefully ignoring springtails of late. The second was the size - only half as big as I would expect Allacma fusca to be. Was I missing something? For this reason, I decided to check the key features:

Yup, Allacma fusca. But why so small? VC55 springtails are still recovering from the drought and heat of 2025 - there are still relatively few adults around (apart from the bulletproof Tomoceridae). Now that the rain is here, things should get back to normal. 

 

Entomobrya petri

McCulloch, J.I. (2025) Entomobrya petri sp. nov.: A new species of springtail found in the British Isles. Soil Organisms 97 (2). https://doi.org/10.25674/476

"A new species of elongate springtail (Collembola: Entomobryomorpha) is described from a churchyard in Edinburgh: Entomobrya petri sp. nov. Microscopic examination of specimens from another site in the UK supports that this new species represents the taxon previously referred to as "Entomobrya nr. imitabilis", which is widespread in the British Isles. As well as that of the examined specimens, the ecology and distribution of the morphospecies generally is discussed."

 

Springtails on NBN

Thanks to the hard work of James McCulloch & Duerden Cormack more than 6,000 springtail records have been imported from iRecord and are now available on the NBN Atlas, bringing the total number of records online to over 26,000.  This is a major milestone for springtail recording and will stimulate further records. 

 

Another instance of DNA not helping

Five years ago I had a crisis of confidence when Peter Shaw published his paper on DNA analysis of Lepidocyrtus - see: Big trouble in Lepidocyrtus. DNA analysis made identification of Lepidocyrtus much worse rather than helping!  While I was trying to find my way through the mess, Matthew Shepherd commented "many soil animals ... don't really fit into the concept of a species", but went on to say "we can still learn a lot from lumping these morpho-types together for recording purposes".  Frans Janssens commented "please continue to record ... based on morphology". Nevertheless I had lost a lot of confidence and so put Springtails on the back burner. 

Recently I worked up the courage to dip my toe in the DNA bathwater again. The Barcode of Life Data Systems (BOLD) project aims to derive taxonomic information from DNA barcodes: https://bench.boldsystems.org   From the BOLD website I obtained a useful result which supported the idea that some questionable Hemiptera morphotypes do indeed seem to be distinct species. Encouraged, I decided to go back to BOLD and try to figure out what I could derive for two of the most problematic Collembola groups. 

Species identification in Isotomurus is problematic because it relies on variable dorsal pigmentation patterns. In conversation Peter Shaw told me that he was planning DNA work on Isotomurus with an aim to review the genus, but sadly that didn't happen. Isotomurus records on BOLD currently consist of 727 records forming 43 BINs (clusters). (The Barcode Index Number System (BINs) clusters barcode sequences algorithmically. Since clusters show high concordance with species, this system can be used to verify species identifications as well as document diversity when taxonomic information is lacking.) A number of the Isotomurus BINs consist of single sequences representing unknown "species". BOLD lists 34 Isotomurus "species". DNA demarcation lines (BOLD BINs) and pigmentation patterns do not fully align. This doesn't really help me but at least it clarifies what the problem is - it's daft to identify morphospecies based on a single variable character such as pigmentation.

So far, so bad, but I also wanted to look at another problematic group, the Katiannidae (which includes Sminthurinus). Here BOLD has 5,250 records forming 294 BINs (clusters), with 51 "species" recognized by BOLD. It's widely acknowledged that the family Katiannidae is a mess and needs revision, but then I stumbled across a paper that I've been ignoring during my Collembola sabbatical: 

van Bezouw, R. F., McCulloch, J., Janssens, F., & Berg, M. P. (2022). An emended description of Sminthurinus lawrencei Gisin 1963, with notes on the identification of black Sminthurinus species. Soil Organisms, 94(3), 127-138. https://doi.org/10.25674/so94iss3id283

The great thing about this paper is that it uses a precise character (chaetotaxy - position and number of setae (hairs) on the dentes), rather than a variable one like pigmentation, to define morphospecies. While chaetotaxy is not a useful field characteristic, the paper also claims that macrophotography can be used to  separate the black Sminthurinus species. While I'm not ready to go back to Isotomurus, it might be time to pay Sminthurinus some attention again. 

 

Finally some good news

2024 was a very sad year when we lost some major figures in the springtail community. Frans Janssens was an enormous help to me when I started recording springtails and I was sad to hear of his passing. I also learned so much from Peter Shaw that I felt this additional loss keenly. Fortunately, 2025 begins on a brighter note with the news that James McCulloch has taken over the UK Springtail Recording Scheme. James is a highly knowledgeable springtail enthusiast, and even better, has already started verifying springtail records submitted via iRecord, a daunting task which has not happened before. All this is very positive for the future and I am encouraged by this positive development.