Brown Tree Ant (Lasius brunneus) Photo by Ryszard at https://www.flickr.com/photos/ricosz/16664758345

Dear Readers, we had a wonderful guided walk in Coldfall Wood yesterday, led by ecologist Russell Miller. We learned all sorts of interesting things, but of course I was most excited by the discovery, in a fallen birch log, of what we think is the nest of the Brown Tree Ant (Lasius brunneus), a most elusive and unusual (and probably under-reported) insect. And no wonder it’s not well known! Usually, the Brown Tree Ant lives inside living oak trees, but it will also live in dead wood, as in this case.

My Ant bible, ‘Ants’ by Richard Jones in the British Wildlife Collection series (highly recommended) describes the species as ‘timid and non-aggressive, and disappears quickly if its galleries are uncovered when peeling bark off old rotten trees’. Much, I suspect in the same way that I would run for cover if a giant alien took the roof of the houses off for a look. Apparently, though the species prefers ancient woodland, it is occasionally found in houses with timber frames, and Jones reports  being given a biscuit tin that had been invaded by the species from a house in Guildford.

The status of this quiet little ant is not clear in the UK – it may well have benefitted, as Jones suggests, from the different management of woodlands since World War II. Previously, woods were coppiced, pollarded and cut for the wood that they produce on a regular basis, but these days such activities are rare, resulting in the deeper, darker woods that we’re familiar with now. This may well have benefited an ant that prefers to live harmlessly in living trees, though it’s fair to bemoan the falling numbers of butterflies who used to benefit from the more open, sunny areas in woods that used to exist. Swings and roundabouts, I guess!

And even life beneath the bark is not without its challenges. There are whole communities of tiny rove beetles and weevils who seem to co-exist with the ants, but there are also other ant species, such as the Yellow Shadow Ant (Lasius umbratus) where a queen will infiltrate a Brown Tree Ant nest. First she will munch a few worker ants – it’s thought that this may change the way that she smells, and enable her to move through the nest more easily. Then, she finds the queen ant and kills her, before starting to lay her own eggs. The workers accept her, because by this time she smells like ‘one of us’. For a while, the colony will be a mixture of Brown Tree and Yellow Shadow workers ants, but, as the former die off and are not replaced because their queen is dead, the nest becomes a Yellow Shadow Ant nest. All these tiny battles going on, unseen beneath a piece of bark!

Yellow Shadow Ant (Lasius umbratus) Photo by By This image is created by user Dick Belgers at Waarneming.nl, a source of nature observations in the Netherlands.