Wych Elm tree 'oozing' liquid

Darren B and Andy M spotted something unusual happening around a Wych Elm tree in Lagden's Grove.  Large numbers of blowflies, wasps, hornets, Red Admiral butterflies and other insects, were gathered all over the bark, spreading right up the trunk of the tree.

In some places, the insects were gathered around dark areas where (presumably) sap was obviously oozing from the bark.  However, in other areas, insects and in particular the butterflies, were also apparently feeding within the cracks and crevices, even though no damage or sap was obvious.

A little internet searching suggested that the tree may have become infected with bacterial wetwood.  The bacteria enter the tree through wounds in the trunk, branches, or roots, and over time  as the infection spreads deep into the wood, high pressure builds inside affected trees from the bacterial fermentation activity.  Eventually, gases and sappy fluids start to ooze out through cracks or wounds on the tree, slowly running down the crevices of the rough bark. Interestingly, bacterial wetwood is more common in years when trees are suffering from drought stress.  

Apparently, affected trees can often recover from this, unless some other infection takes hold.  Either way, this was clearly a welcome bonanza for those insects happy to feed on the sugary liquid.

Wasps taking advantage of liquid oozing from a crack in the Elm bark

One of several Red Admiral butterflies, also apparently feeding on the bark, 

reaching into the crevices with their proboscis