|Bracket fungi on standing deadwood|
|Wild Service tree with the oak behind. The red arrow indicates the branch with a sap-run.|
|A hornet on the underside of the branch|
|Three Red Admirals fighting above while one feeds on the underside. Also note the large flies on the upper surface which may be feeding or basking.|
These are only a few examples and there are many others, especially among the hoverflies as the numerous mentions of sap-runs by Rotheray & Gilbert (2011) can testify, including the danger of becoming trapped in sticky fluid that eventually becomes amber. As noted by Kirby (2001), this highlights the importance of sap-runs, along with many other features of trees (rot-holes, dead branches, ivy) that are sometimes removed as signs of 'ill-health', such as by being selectively removed during woodland thinning rather than being selectively retained. In fact, it seems clear that larger and longer-lasting sap-runs support more diverse species assemblages and so trees with large, deep injuries forming sap-runs should be retained just like those with large dead-wood features. It means overturning some of the received (but erroneous) wisdom ingrained in aspects of woodland management, but structural diversity is of key importance and the countryside isn't meant to be neat!
Fry, R. & Lonsdale, D. (eds) (1991). Habitat Conservation for Insects - A Neglected Green Issue. AES, Middlesex.
Kirby, P. (2001). Habitat Management for Invertebrates: A Practical Handbook. RSPB, Sandy.
Rotheray, G.E. & Gilbert, F. (2011). The Natural History of Hoverflies. Forrest Text, Tresaith.