Revisiting the Formica Ants in our Apple Tree

2016 July 19

Previously, I posted pictures of ants that had taken up residence in one of our old, partially-hollow apple trees. They had stuffed the trunk with bits of grass, wood chips, and similar debris, and taken up residence in it. I had thought that the nest had died after some bluejays used it for an “anting” site, but on July 9, 2016, we saw that it was still a vigorously going concern.


Here they are a bit closer:


Of course, still pictures really don’t do justice to an active ant nest. So here’s a short video to get the proper impression of the way it was seething with ants:

They were still actively adding thatch to the nest. The thing is, the cavity was a good five feet up in the tree, so they were carrying the thatch right up the side of the tree trunk. Here’s one that was not only carrying a stick many times longer than herself, but was also climbing vertically up a tree trunk!

They were clearly putting a lot of effort into carrying the thatch up the tree, so it must have been of use to them. The main thing is that it fills in the tree cavity so that, instead of being just on the sides and bottom of the hole, they can occupy its entire volume. The pieces of thatch probably also help to shed rainwater, and make it more difficult for predators to get into the nest proper.

So, anyway, these are pretty clearly one of the species in the Formica rufa species group. This is a collection of numerous very similar species found in both North America and Eurasia, some of which make heavy use of thatch to build their nests. Normally I see these as mounds, this is the only one I’ve seen where they are stuffing an upright tree. Anyway, ants like these are generally pretty predatory, and I expect that they are doing a good job of clearing out caterpillars from the apple tree.

Not to mention, keeping children from climbing the tree. They are very pinchy.

2 Responses
  1. Anne Bingham permalink
    July 19, 2016

    All the trendy trees are going with granite ants these days. Formica is just so 1970.

  2. Carole permalink
    July 19, 2016

    Your ant carrying the grass reminded me of the grass-carrying solitary wasps that have moved into the openings in our new outdoor bar stools. The grass must be 4x longer than the wasp. They fly to the top of the stools and use it as a divider between cells.

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