WOODLAND AND HEDGEROW - DEAD WOOD




 

 

Management techniques in the aftermath of the storm of 1987 were not perfect but as regards dead wood they were better than ten or 15 years earlier, when just about every flattened or damaged deciduous tree would have ended up burned or ground into chippings.

The position is improving all the time and nowadays dead wood is becoming quite fashionable deservedly so, given its importance for around 1,800 species of invertebrates which use the substance, nearly half of them rare or threatened. By the same token, increase the dead wood and you can also help increase the number of birds.

There are various ways of creating dead wood to last. Naturally, there are decay and the effects of wind or lightning. Artificially, there is the felling or pruning of a tree followed by allowing the cut wood to lie where it lands.

The latter happened with the Beech tree (Fagus sylvatica) featured on this page. Standing at 30 metres and close to a busy road, a house and two public footpaths, in the early 1990s it was badly affected by Giant Polypore fungus (Meripilus giganteus), which made it unsafe. The council felled the tree but left the trunk lying in two sections. Beech is a relatively soft wood and it didn't take long for various invertebrates to take advantage of the new resource.

By 2009 the wood was shaded out and the wildlife was seriously reduced but the flow had reached a high point between 2005 and 2007 when the most obvious residents were solitary digger wasps from the Crabroninae family. Ectemnius cephalotes, one of ten in the Ectemnius group in the UK, led the way. Ectemnius wasps are pretty common; all prey on Diptera (flies) of various families on which their larvae feed, and all but one nest in rotten wood.

Ectemnius cephalotes (15mm), though not social as regards breeding methods, can be social in nesting colonially, as occurred in the Beech, where they were visible from June to early October. There was one main entrance with anything up to eight females using it, who bore lateral tunnels with separate cells capable of containing up to a dozen prey items apiece. The borings below the entrance were testimony to the size of the colony. The males, as usual, are smaller and play no part in breeding once mating has occurred.

The females caught prey some distance from the beech, and generally flew straight into the nest at speed with it, an action requiring perfect judgement and one that presents a remarkable sight to an observer, albeit not quite so stunning as another digger wasp, Cerceris rybyensis, flying into its sandy burrow with mining bees. Sometimes the Ectemnius cephalotes settled, especially if another was exiting the nest site while they were trying to enter.

Two other species of Ectemnius were seen using the beech Ectemnius continuus (12mm) and Ectemnius lituratus (13mm), though the latter was in a different section of trunk. Both also burrow out multi-celled nests but catch slightly smaller prey than Ectemnius cephalotes.

Other species using the trunk for one reason or another in this period unfortunately the nesting area was dug out by kids in 2008 included the nesting wasps Crossocerus podagricus and Stigmus pendulus, the lovely Small Magpie Moth (Eurrhypara hortulata, wingspan 35mm), which bred on nearby nettles, and the large Ichneumon wasp Dolichomitus imperator (35mm), which is shown using its long, needle-sharp ovipositor to probe for weevil larvae in which to lay eggs. A scarce fly, formerly RDB2 but seemingly increasing in numbers, was very evident on the surface in 2006. This was Paraclusia tigrina (7mm), a fly with red-brown the predominant colouring whose larvae are believed to develop in moist rotten wood, particularly Beech. The log offered a perfect habitat.

To give an additional indication of the variety of species associated with dead wood, two invertebrates photographed within 50 metres of the log have a link with this habitat. The impressive and nationally scarce hoverfly Criorhina ranunculi (14mm) is a bumblebee mimic whose larvae have been found in Beech roots and in rotting wood from Beech and Birch (Betula spp).

The pictured Tumbling Flower Beetle (Mordellidae sp, 10mm) has a distinct pointed abdomen often found in the genus. Many of the larvae develop in dead or dying deciduous wood. The adults are decidedly lively and take their name from the fact that they tend to somersault off flowers in the blink of an eye if approached.

Similarly, logs and pieces of wood or bark of all sizes left lying on the forest floor afford perfect shelter for creatures which do not want brighter or drier conditions, including Woodlice, Centipedes and Millipedes.

The former are crustaceans, the latter two arthropods which emerge into the open at night and hunt smaller invertebrates. They have no eyes, relying on touch and vibration to identify prey, which is killed by poison injected through the front legs modified as fangs. The commonest centipede, found under a piece of wood from the beech, is Lithobius fortificatus (30mm), a fairly chunky species.

On dead wood (Oak) not far a way in 2009 I found a remarkably rare fly, Rainieria calceata (12mm), which is a Red Data Book 1 species found at fewer than ten places in Britain including Windsor Great Park and Burnham Beeches. They have been discovered in a couple of other places in Surrey in recent years so maybe they are not quite so endangered as their status suggests.

The species is one of the co-called Stilt-legged Flies, all of which have long legs. The larvae feed on decaying matter and adults are found in woodlands. One noted piece of behaviour is lifting the usually well-marked forelegs into the air. The reason for this may be connected to imitating aculeate antennae and deterring predators but that's far from certain.

Images Jeremy Early. All rights reserved.

In 2013 I published My Side of the Fence the Natural History of a Surrey Garden. Details may be found, and orders placed, via this hyperlink My Side of the Fence. In November 2015 Surrey Wildlife Trust published the atlas Soldierflies, their allies and Conopidae of Surrey, jointly written by David Baldock and me. Details are on this web page: Atlas.

WOODLAND AND HEDGEROW: Trees & Fungi . Dead Wood . Bluebells . Flora . Mistletoe . Birds . Beetles . Bugs .
Butterflies . Bees . Cuckoo Bees . Bee Parasites . Solitary Wasps . Sawflies . Parasitic Wasps . Hoverflies . Other Flies . Spiders