Entomobrya Identification Guide

The genus Entomobrya are arboreal species with four antennal segments and elongated abd4. Entomobrya species are identified from dorsal pigmentation patterns. Unlike other groups, e.g. Tomoceridae, Entomobrya species are unscaled, so pigmentation patterns are more reliable.


Entomobrya albocincta has a broad pale band on the thorax:



Entomobrya intermedia has a characteristic broken “U” (the corners are missing) on abd.5/6 and a “W” across the top of abd.4.



Entomobrya multifasciata:



Entomobrya nicoleti has only two dark spots on the sides of abd4:



Entomobrya nivalis has no inverted V shape (the central part of the W pattern in E. intermedia) at the top of abd4:




Other Identification Guides: https://collembolla.blogspot.co.uk/p/identification-guides.html

Isotomurus Identification Guide

Isotomurus can be separated from Desoria and Istotoma by the configuration of the ocelli in the eyespot, but also by the distribution of long setae (macrosetae) on the body:

• Istotoma: macrosetae on all body segments
• Isotomurus: macrosetae on last few abdominal segments only
• (Desoria: no macrosetae)

Many species in this genus were badly confused in the past and lumped together as "Isotomurus palustris". In recent years they have been separated into distinct species. Adult specimens have characteristic pigmentation patterns which makes identification easier than some other groups (juveniles are paler and often difficult to identify until they develop the characteristic patterns).

Mucro:
Desoria - mucro has four teeth but does not possess a lateral seta, apical tooth is large.
Isotoma - mucro has three teeth.
Isotomurus - mucro has four teeth, apical tooth smaller than the others:




Isotomurus palustris has a near continuous dorsal line and fainter lines on the sides of its abdomen (juveniles are paler); mucro does not have a lateral seta. Species boundaries in Isotomurus are very difficult to determine and I. palustris is best recorded as I. palustris sensu lato unless there is very strong evidence to the contrary:





Isotomurus pseudopalustris has three macrosetae in triangular configuration on sides of abd4. Dark broken dorsal midline with two characteristic pale dots either side of midline on abd4. Adults have some pigmentation on sides of abdomen, juveniles are paler:




Isotomurus unifasciatus has a continuous dark line down its midline but is otherwise uniformly pale:




Isotomurus maculatus has a distinctive dorsal pattern resembling a backward facing crown;
Isotomurus plumosus has both an unbroken dark midline and lateral stripes:





Other Identification Guides: https://collembolla.blogspot.co.uk/p/identification-guides.html

A Wildlife Hero

One of our local wildlife heroes has spent days sorting through a giant dungheap in Leicestershire. But this isn't any old dungheap, oh no, this is a very special dungheap. Most cattle these days are treated with a wide variety of drugs, including antibiotics but also a range of powerful and persistent anti-parasitic compounds. There are arguments to be made around animal welfare, but the effect of these drugs mean that dungheaps are almost devoid of their traditional fauna - the good guys get wiped out alongside the parasites. And of course that means less food for birds and bats. But this dung heap was produced by one of the tenant farmers of the Wildlife Trust*, and under their guidance very few drugs are used on this farm. And it "only" takes someone with good knowledge to sort through the dungheap to see the results. So far, the Wonderheap has produced several new county first beetle records. And of course, there are springtails in there too which they were kind enough to pass on to me for identification.

The predominant species was Pogonognathellus longicornis, with good numbers present. Also abundant were Isotoma viridis:




and Isotomurus pseudopalustris:


Adult


Juvenile


I've never sampled dungheaps for springtails, but I'll have to get around to it at some point. In the meantime, I'm grateful to the heroes who do.


* To be accurate, produced by his cows :-)

Sminthurinus aureus

Sminthurinus aureus is a very common terrestrial springtail, less than 1mm long. It is particularly abundant on the underside of fallen leaves in autumn (as are other globular species). As the names suggests, it has an overall golden colour with no clear banding. Sminthurinus aureus has the 'small abdomen' (the animal's "tail end") wholly fused, while other UK Sminthurinus have a visible division between segments 5 and 6. The fourth antennal segment (ant4) is not subdivided.



Female:




S. aureus comes in a variety of colour forms with varying degrees of dark pigment, e.g. form ochropus:

08.04.18 - Burroughs Wood

This trip was my first to a new site which consists of two parts, half ancient woodland and the other newly planted areas approximately 20 years old. This visit only covered the old part, which was interesting. Although there are few large old trees there is a very good mixture of species, nearly all of which have been coppiced repeatedly, with some coppice of the stools several metres across. Importantly, there was lots of old dead wood on the ground! I mostly sampled under logs and was delighted to find Diplura and Symphyla abundant. Springtails were also abundant, mainly Lepidocyrtus lignorum and Pogonognathellus longicornis. Of most interest were a few Entomobrya nivalis (above), shaken from terrestrial moss. Nivalis means "of the snow", so having looked for this species all winter, I find it both amusing and ironic that the first time I find it is when the snow is gone.

Dicyrtoma fusca

Members of the Dicyrtomidae are characterised by having a very short fourth antennal segment. Dicyrtoma fusca is the only UK species in this genus (c.f. Dicyrtomina - minuta, ornata, saundersi).

Dicyrtoma fusca is a small globular springtail (1-2mm) which varies considerably in colour from a dark maroon red to a paler yellow form, the mottled patterning also varies:





These forms are known as Dicyrtoma fusca var.1. There is also a much rarer melanistic dark (almost black) form, Dicyrtoma fusca var.2 (not known from VC55), and a leucistic form with dark ocelli on a pale eyepatch, Dicyrtoma fusca var. rufescens:

29.03.18: Cademan Wood - Springless Springtails

Cademan Wood is a very varied site with stands of broadleaved trees and conifers as well as outcrops of lichen and algae-encrusted Precambrian rock that deserve further exploration on future visits. On this trip we concentrated on the stand of mature Beech at the north end of the site. Here Pogonognathellus longicornis was the predominant species in the Beech leaf litter with large numbers present.

There are also mature Scots Pine in this part of the wood and I sampled the trunks and under the bark. The predominant species was Entomobrya albocincta, present in good numbers. Lepidocyrtus lignorum and Hypogastrura sp. were also found. Of most interest was a single specimen of Anurophorus laricis, a species I have not recorded in VC55 previously, although it is regarded as a common arboreal species:



This is an interesting springtail - it doesn't have a spring (furcula)!

• "Dark blue" with 8+8 ocelli but these are difficult to see among the dense pigment on the head. Specimens need to be cleared to see the eyes.
• Does not possess a furca and there is no empodial appendage on the foot - important in distinguishing this species from other (rare) members of the genus.

See: http://urweb.roehampton.ac.uk/collembola/taxonomy/(238ANlar).html

Southern Bristletail, Dilta hibernica?

I recently came across a colony of bristletails so I took the opportunity to examine a few, which I tried to key out using:
Delaney, M.J. (1954) Handbooks for the Identification of British Insects. Vol. I, Part 2. Thysanura and Diplura. Royal Entomological Society, London.

It was quite easy to get these to the genus Dilta based on the conformation of the ocelli:




After that, it got difficult/impossible. In reality, based on the UK distribution this has to be the Southern Bristletail, Dilta hibernica (because it can't be Dilta littoralis in Rutland as this is a marine species), but it's impossible to confirm this as identification of Zygentoma is based on adult male specimens - females and juveniles cannot be identified to species level, but most if not all populations are parthenogenetic (no males!).

None of the specimens I examined were adult males, so I could well be on a loser with this. The reason I would like to record this species rather than just walking away (apart from taxonomic completeness) is because these are relatively large and quite visible arthropods and I'm not the only person who will have seen these. I could just call it "Dilta sp." or "agg.". The alternative would be to list it as Dilta hibernica sensu lato, but in reality, "sp." would be more accurate if less precise.

Diplura - Good News, Bad News

When I wrote about Diplura ("two-pronged bristletails") last week, I noted that their appearance is seasonal, peaking in spring and autumn. Ever since the snow melted I've been checking the locations in my garden where they always appear each year, but hadn't found any so far. On Sunday however, I found good numbers (together with Symphla) at Burroughs Wood:


Working from: Delaney, M.J. (1954) Handbooks for the Identification of British Insects. Vol. I, Part 2. Thysanura and Diplura. Royal Entomological Society, London, they seem to key out as Campodea staphylinus:

Mesonotum with postero-lateral macrosetae = Campodea:


Abdominal tergites 6-9 with antero-lateral macrosetae. Length 3·9-4·6 mm = C. staphylinus. "Common throughout British Isles":



But that's where it gets difficult. I'm far from confident in this identification. On Diplura, Barnard says "Currently 11 species have been recorded from Britain, all in the genus Campodea, but there is little information on their status and distribution. In recent years the taxonomy of Campodea species has been modified by European workers and it is no longer clear exactly which species occur in Britain, nor how best to identify them. Consequently the group is in urgent need of revision in this country. Delaney's (1954) key cannot be relied upon because of these taxonomic changes and a new handbook is needed for this small yet significant group" (Barnard, P.C. (2011) The Royal Entomological Society Book of British insects. John Wiley & Sons. ISBN 1444332562). However, I have a problem with that. There are certainly problems with the Delaney key, but in the absence of anything else, surely this has to stand rather than just saying "Nope, not a clue"?

There are three ways to deal with this (apart from resorting to DNA typing which is beyond the reach of virtually everyone):

1. Only accept definitive records. This means that essentially no-one will be able to record these species and we will remain ignorant about their populations.
2. Record to genus level only - Campodea sp. However, these are common soil organisms so this will only capture low quality aggregated data about populations.
3. Accept well-meaning but likely misidentified specimens as Campodea staphylinus sensu lato, etc. This is unsatisfactory also because it will contaminate the records and make it difficult to future workers to interpret.

So I'm stuck and unsure how to proceed...

Playtime with Springtails

I've been experimenting with different materials to make corrals for photographing springtails:



I started by using Blu Tack, because I had it to hand. Blu Tack works OK, but if you stretch it, it gives off sticky fibres which animals get stuck on (it is, after all, designed to stick things).

I decided that Plasticine might be better, but I couldn't find any. What I did find was Play Doh, which is slightly better than Blue Tack and is nice and soft so it's easy to press the slides together to get just the right depth. However, it does leave a sticky residue on slides - and I have watched springtails trying to eat it! I finally found some Plasticine. This is probably the best of the three, although it is quite stiff and needs quite a lot of pressure to get to the right depth.

Conclusion: Blu tack, Play Doh and Plasticine all work - give it a go and decide which you like best.

01.04.18 - Skeffington Wood

As part of the NatureSpot Mind the Gap campaign, I made the effort to get out to Skeffington Wood, even though the weather was less than inviting. One of the reasons there are gaps in the NatureSpot coverage is because access is difficult in some of these areas. As part of the Leighfield Forest SSSI, Skeffington Wood is seriously under-recorded, but at least access is easy because there is a road ("Not suitable for motor vehicles") running though it. This was very much a reconnaissance and only a first effort at recording. One interesting difference between two very similar woods, close in distance and one week apart, was that in contrast to my last trip, there was a complete absence of Symphylans at this site. In my opinion, this is because while there are some logs on the ground, the timber is very fresh and there is no rotting wood around. The whole wood is very "tidy", heavily managed for pheasant shooting and ill-served as an SSSI.


Sampling under bark/logs on the ground, Orchesella cincta was predominant, and I also recorded Tomocerus minor, Isotoma viridis and Lepidocyrtus lignorum:


Lepidocyrtus lignorum, scales on ant1+2


Brushing from tree trunks Orchesella cincta was again the predominant species. In some cases there were patches of moss on the ground and sampling from these Entomobrya albocincta was abundant, with Lepidocyrtus lignorum also present, and Isotomurus unifasciatus:





To my knowledge, these are the first records of springtails from this site.

The Joy of Bristletails

Although I called this blog "Springtails of Leicestershire and Rutland" that's only because it's a better title (in my opinion!) than "Springtails, Bristletails and various other soil arthropods I come across while I'm looking for Springtails in Leicestershire and Rutland". However, it is also my intention to work on the massively-neglected bristletails, and I've been putting some effort into this over the last month. This post is very much an introduction and a summary of what I have learned.

Bristletails (or Archaeognatha) are the most primitive of living insects, having existed since the mid-Devonian period. These cryptic, semi-cylindrical organisms are nocturnal and typically hide in crevices during the day, or are soil organisms living in the dark without eyes. About 500 species are known worldwide and they live in diverse habitats, from the sea shore to high altitudes in the Himalayas. Bristletails are herbivores and detritivores (detritus feeders). While they are not predatory, some species will scavenge the remains of arthropods. Some species of Symphyla can be agricultural pests, multiplying to high numbers and feeding on the roots of plants. Edwards quote densities of 88 million per acre (= 21,000 per square metre) in agricultural land (Edwards, C.A. (1958) The ecology of Symphyla. Entomologia Experimentalis et Applicata, 1(4), 308-319). The highest densities occur in light, humus-rich soils with significantly lower abundance in heavy clays (like Leicestershire!). The Symphyla are seasonal, with the highest numbers occurring in spring and autumn (related to soil temperature and moisture), although apparent numbers are affected by seasonal vertical migration in the soil (less so on clays where they tend to be restricted to the surface).

Phylum Arthropoda
Subphylum Hexapoda (from the Greek for six legs):
Class Insecta:
Order Zygentoma (formerly Thysanura) — silverfish and bristletails
Order Archaeognatha
Class Entognatha:
Order Diplura — "two-pronged bristletails" (Symphyla)

Bristletails are in the Orders Zygentoma (formerly Thysanura), the silverfish and firebrats; and Archaeognatha.
Etymology: Thysanura comes from the Greek thysano, which means fringed or bristled, and ura, which means tail. Thysanura, therefore, means "bristled tail," which is a reference to the caudal filaments characteristic of these organisms. Zygentoma comes from the Greek zygon, which means bridge. This refers to the unfounded idea that this group of insects is an evolutionary link (a bridge) between other orders of insects, particularly the insects.


Image source: https://www.phrygane.tk/early-cretaceous/earliestlnsects.html


So what's the problem - why is this group so neglected in terms of biological recording? There are two problems. First, the occurrence of bristletails is quite uneven, with high numbers in some locations and very low numbers in others. This is in contrast to springtails, which are much more evenly distributed. Delving deep into the literature, more than one PhD project appears to have fizzled due to the problem of finding enough specimens to do anything useful with. Edwards laments the fact that the taxonomy of this group has been buggered up by so many taxonomic descriptions being based on single (misidentified) specimens! However, there's a worse problem - identification to species level. Most bristletails are relatively easy to get to genus level, but that's where the problem starts. Identification of Zygentoma is based on adult male specimens - females and juveniles cannot be identified to species level. And then you learn that some species hybridise extensively with others and at least some populations if not species are parthenogenetic (no males!) ... (Dejaco, T. et al (2016) Taxonomist’s nightmare... evolutionist’s delight: an integrative approach resolves species limits in jumping bristletails despite widespread hybridization and parthenogenesis. Systematic biology, 65(6), 947-974). The Diplura present a different challenge. Here some taxonomies have been based on morphological characters, including the number of segments, length of antennae, etc, but this changes as they mature. Symphyla hatch with 6 legs and relatively short antennae but pairs of legs and antennal segments are added with each moult. Identification can therefore only be achieved with adults, so the first stage with these organisms is always to count the number of legs!

Overall then, quite a challenge, and I can see why many people have shied away from this group. What a bunch of wimps!
;-)


Literature used:

Delaney, M.J. (1954) Handbooks for the Identification of British Insects. Vol. I, Part 2. Thysanura and Diplura. Royal Entomological Society, London.
Available for download from the R.E.S. website. A useful guide at least to genus level but somewhat superseded by the Work of Edwards.
Revised provisional key, based on Delaney, is available online courtesy of www.bristletail.net:
http://www.bristletail.net/british_isles/id/id.html

Edwards, C.A. (1959) Keys to the genera of the Symphyla. Zoological Journal of the Linnean Society, 44(296), 164-169.
A useful overview to the genera, well illustrated and relatively accessible.

Edwards, C.A. (1959) A revision of the British Symphyla. Proceedings of the Zoological Society of London, 132: 403-439.
The most detailed guide to the Symphyla, but not for the faint-hearted :-)

Jordanathrix nr. superba

Formerly designated Calvatomina nr. superba, Jordanathrix nr superba resembles but is distinct from Dicyrtomina superba from New Zealand (which does not occur in the UK). Thought to be a relatively recent introduction to the UK, first recorded about 10 years ago. Similar to Dicyrtomina ornata but in D. ornata the eyepatch is uniformly dark; in this species the dark ocelli are on an lighter eyepatch with a reddish background colour.



Detail of eyepatch.



Pigment patch on abdomen - similar to D. ornata.



Female?



Male - genital papilla visible below abdomen, smaller than female.