Tiny denizens of the rot-hole

What with winter keeping most invertebrates out of sight, it's been a while since I wrote much of an entomological nature, but yesterday was a fine opportunity to head up to Beacon Hill nature reserve to see what was about. As well as chalk grassland (which will be more interesting when in flower), there is an interesting stand of beech woodland and associated scrub, including an ecologically important resource of dead wood (standing and fallen) and old mossy trees.

The base of a mossy beech tree.

These features mean that there is habitat for many fungi and dead-wood invertebrates and the evidence is everywhere - beetle boreholes (some opened by woodpeckers, one of which could be heard clearly in the woodland), wood in various stages of decay, insect-feeding birds such as a treecreeper (Certhia familiaris) and an intriguing-looking rot-hole with a large fungus and a tuft of hair poking out of it...

Rot-hole with fungus and tuft of hair

Looking inside, it had been lined with moss and hair, and was clearly a nest or roost of some sort, either of a bird or small mammal, and the fungus is (I think) an oyster mushroom Pleurotus ostreatus - if any mycologists would like to correct me on this, please do!

The inside of the rot-hole; at the base of the fungus, a layer of moss-and-hair bedding.

So, sample-pot in hand (like any good ecologist!), I took a pinch of the mossy bedding, including some soil/decayed wood from directly beneath it - after all, there are plenty of under-recorded parasites that live in vertebrate nests and you never know what you'll find. Back home, it was time to check what I'd found; some of the small inveretebrates such as Collembola (springtails) hide very effectively in material like this, so I find that adding some water to the sample in a watch-glass causes them to float to the surface and become easier to see. Indeed, doing this brought up a cluster of the common springtail Ceratophysella bengtssoni which can sometimes be found in large aggregations on the surface of soil and puddles, but may well still have been hibernating given the cold night-time temperatures at present.

Several Ceratophysella bengtssoni from the nest sample

These weren't the only springtails - Lepidocyrtus cyaneus and Neanura muscorum were also present, as was Tomocerus vulgaris from mossy dead-wood of a nearby tree. The samples included quite a few empty moulted skins, suggesting that these are not solely hibernation sites, but places where active feeding and growth occur - unsurprising as they mainly feed on fungal hyphae and decaying plant material (no shortage in this sample location). They are also an excellent group to look for in the winter as they can be found throughout the year - if you are interested in the UK species, Hopkin (2007) is an excellent place to start. However, Collembola are not the only soil/leaf-litter animals to be found. Hidden among the tangle of hair (mainly sheep I think) and plant fibres were two shed skins of an oribatid soil mite.

The shed skin of an oribatid soil mite

Oribatids are beyond my identification skills (I don't even know anyone who can ID them, though I do have a go at halacarids occasionally), but the shiny bulbous shape, the pointed mouthparts and the leg attachment points are all visible here. Though poorly known outside the realm of specialists, these mites are important in the decay process, feeding on a wide range of plant, animal and fungal organic material, with a minority being predatory - in fact they break down and process soil material in a similar way to earthworms even if they aren't as familiar or well-understood/studied.

Another species, common if often over-looked, and mainly found under bark or logs in woodland is the spotted snake millipede Blaniulus guttulatus. It is often considred a pest (e.g. in allotments) but probably only enters crops when damage has already occurred, such as by a 'primary' pest or some other mechanical means. They grow to around 20mm in length and are white with rows of red spots along the sides. The specimen I found however was a juvenile no more than about 3mm long (with few segments/spots), and the first early stage I've seen of this species.

Juvenile Blaniulus guttulatus

So, a few interesting finds - common species (no idea about the oribatid) but indicative of the small and often un-noticed soil/dead-wood fauna. Interestingly there were no mammal/bird nest-dwelling species (such as ticks or fleas), and no indication of exactly what had been using the hole - however, the presence of fine hairs and small dark elongate faeces, plus a lack of even small feathers suggest a mammal, presumably a rodent, rather than a bird.

Reference

Hopkin, S.P. (2007). A Key to the Collembola (Springtails) of Britain and Ireland. FSC, Shrewsbury.

Uninvited guests in the nest

Having recently described the unexpected discovery of an occupied song thrush nest and the subsequent successful fledging of the chicks, being a bug-nerd at heart, I felt the need to have a closer look at the nest itself once it was no longer in use to see if any small invertebrates lay within... However, this isn't just random nosiness - there are many parasites that live in the nests of birds and mammals, and it's also the type of place where overlooked species may be found - after all, not that many people are likely to check. So, white tray in hand I began to sift...

The first species to popout was a barklouse or psocid (Psocoptera). This group contains many small species that are associated with bark, dry plant material and so on. I won't go into too much detail here, but the specimen was about 1.5 - 2mm long, variably brown with yellow and brown markings on the head, and the wings held like a shallow roof over the abdomen. Helpfully (as these tiny creatures can be tricky), the forewings also had a pattern of spots that indicated the genus Ectopsocus. As it happens, this pattern is quite strongly diagnostic and as you can see below, the spots are at the end of the wing veins and extend along them so are about twice as long as wide. This provides an identification as E. petersi - an interesting find as it is probably under-recorded, having previously been placed in the 'E. briggsi' group of similar species. However, if any psocid specialists are aware of further taxonomic changes, please do let me know.

Forewing of Ectopsocus petersi

The second species was about the same size (1.5 - 2mm), but quite different in structure - as well as the prominent bristles, it also had a relatively large ventral spring joined to the rear of the abdomen - clearly a springtail (Collembola).The blue-grey colour, which I admit was clearer in the specimen than the photos below), and other features of the ocelli, bristles and spring, plus a dark spot between the antennal bases, suggest that it is Entomobrya lanuginosa (E. myrmecophilus is associated with ants, rare and with longer bristles, while Willowsia have leaf-shaped scales rather than the covering of bristles). This is usually coastal, but inland sites are known, and a bird nest seems perfectly reasonable for a species that can be found in dry, sheltered locations.

Entomobrya lanuginosa

Close-up of Entomobrya lanuginosa

So, an urge to investigate, and a bit of work, turned up a couple of unexpected species. Possibly not as immediately engaging as nestlings becoming fledgelings (though, my bug-nerdiness means I do like them pretty much equally), but as always, species records are valuable, especially for under-recorded taxa.

References

Hopkin, S.P. (2007). A Key to the Collembola (Springtails) of Britain and Ireland. FSC, Shrewsbury. The current standard work for UK species - excellent.
New, T.R. (2005). Psocids: Psocoptera (booklice and barklice) (2nd ed.). Handbooks for the Identification of British Insects 1(7): i-iv, 1-146. Also the current standard work for UK species - also excellent.