Under the skin of a sycamore

Thursday's Guardian Country Diary is about the remarkable range of small invertebrates that live under the flaking bark of old sycamore trees.

When the bole of an old sycamore tree expands the old rigid bark cracks and begins to curl at the edges, while ....

.... a fresh, new layer of bark forms underneath. It might not look very attractive but these bark flakes, some as large as a slice of toast, take a long time to fall off and while they are still attached harbour a remarkable fauna of small invertebrates underneath. Here's a selection, most of which I've yet to ID.

Millipedes, a hatched moth pupa and some unidentified cocooons 

Lots more millipedes - these were just a few from under two bark scales - if this sample is representative there must have been hundreds sheltering under the bark of this tree

A minute scarlet mite

A rather beautiful little money spider, Gonatium rubens

A huddle of earwigs ....

... that raised their tail forceps in defence when they were suddenly exposed to the light. Male left, female on the right.

A spider that lives in a silken tent under the bark

Lots of slugs in areas where the bark is permanently damp, where rain water trickles down the tree trunk ..

.... together with snails ......

...... and woodlice

Another moth pupa, that looks as though it hatched successfully.


Sycamore sits low in the league table for tree foliage that supports insect biodiversity - a 1961 research paper on the subject found only 15 species, compared with the 284 hosted by oak (click here for details). But a quick look under the flaky bark of old sycamores casts them in a more favourable light, as a sheltered habitat for a host of invertebrates. 

The few examples shown here were just from a height that I could reach - there may well be a different array of species higher up the trunk and the hosted species most probably vary depending on the aspect (sunny & south facing or shaded & north-facing). Moisture must play a role too because there are well defined runnels where rainwater flows down the trunk from the branches and the bark there is always moist and often very wet. All in all, flaking sycamore bark is probably quite a complex habitat, with many interesting interactions between species that inhabit it.

Exploring the undergrowth

I spent a couple of hours last week, on a warm, humid afternoon, exploring the undergrowth at Deepdale Nature Reserve in Barnard Castle. The boggy ground on either side of the footpath was overgrown with butterburr leaves, meadowsweet, vetches, red campion and docks and was seething with insects and spiders.  These are a few that I managed to capture on camera. 

Earwig  - for more about earwigs click here

Female scorpionfly

Male scorpionfly - for more about scorpionflies click here

The beautifully iridescent green dock leaf beetle  - for more about this species click here

A sawfly that I haven't managed to ID for sure yet - for more sawflies click here 

A spider, Tetragnatha extensa, with a golden abdomen. For more spiders click here.

A very bug-eyed mayfly - possibly Ephemera danica. For more on mayflies click here.

A common green capsid bug Lygocoris pabulinus - for more on capsid bugs click here

A staphylinid beetle stretching its wings....

..... curling up its tail in characteristic defensive mode ....

..... and with its wings packed away, showing the extremely short wing cases. For more staphylinid beetles click here

Seeking Shelter ....

Now that the nights of growing colder a steady trickle of refugees are finding their way into the house from the garden. This female earwig is the latest arrival. 

For more earwigs, click here 

Earwigs very rarely unpack their elaborate fan-shaped wings and fly but when they do they are truly beautiful - take a look at this link!

Common

Buttercups are amongst the commonest of all wild flowers and tend to be taken for granted because of that, but they represent a vital, reliable resource for wildlife at the bottom of the food chain. All that pollen supplies food for an amazing array of small insects. 

This young earwig, was nibbling buttercup petals....

............ while this unidentified beetle was feeding on the stamens........

.... and this hoverfly was making a meal of the pollen.

Understandably, naturalists tend to be obsessed with rarities, but it's the common stuff that's really important when it comes to maintaining the stability of  ecosystems.

Feeling the Pinch: Earwigs

I found this fine specimen of a male earwig Forficula auricularia under a rotten log today. You can tell it's a male by the curved pincers on the tail - the female's are much straighter. Earwigs can fly and have exquisite fan-shaped wings but they are tightly stowed away under those little wing cases and are very rarely unpacked. When this one suddenly found itself in the daylight its first instinct was to ....

... crawl into a crevice, so that .....

... only those tail pincers protruded, capable of delivering a painful nip - although their other purpose is to clasp the female's pincers during tail-to-tail mating. Somewhere the female would have been hiding away guarding her eggs through the winter and when they hatch in spring she'll continue to guard the young during their early stages of growth - compared with most insects, earwigs are very attentive mothers.

Earwigs

If you grow dahlias or chrysanthemums for exhibiting in flower shows then this little insect, the earwig Forficula auricularia, is probably your mortal enemy. Earwigs like to rest with their flattened bodies concealed in crevices and the space between closely-packed flower petals is perfect. Unfortunately, while they’re there they tend to nibble the petals. But there is a more endearing side to earwig behaviour; unusually for insects, the females show strong maternal instincts towards their eggs and young. They lay their eggs in late summer and guard them through the winter, constantly licking them to keep them free from fungal infection, and then they feed the infant earwigs through those hazardous first days of life. The earwig in the picture is a male, identifiable by those large, curved tail forceps which are used for defence. When they’re threatened, as this one was, they raise their tails like scorpions, forceps at the ready. Females have straighter, more slender forceps and the other purpose of these organs is for gripping one another, during tail-to-tail mating manoeuvres. Earwigs can fly, but rarely do so. Behind the head there are two sets of wings. The front pair is short and rectangular and probably mainly functions to provide rigidity for the much larger, fan-shaped hind wings. Stowing away the large hind wings is a masterpiece of packaging that involves intricate folding, so maybe it’s not surprising that earwigs rarely take flight. You can find some superb videos of earwigs mating, hatching, defending their eggs and moulting at http://www.arkive.org/common-european-earwig/forficula-auricularia/video-09e.html