More arboreal ants

two ants on branch
Two ants from the first nest – a soldier (above) and a worker

Frangipanis are deciduous tropical trees with – as everyone knows – beautiful flowers, and they are deservedly popular in Townsville gardens. A few days ago I was trimming small dead branches from ours and was vividly, and almost painfully, reminded of the fact that dead branches are hollow and nature abhors a vacuum – that is, small creatures enthusiastically adopt hollow branches as nests.

The creatures in these branches were ants, and I found two different species. Two residents of the first are shown above and yes, they are big ants. The soldier must have been about 15mm long and it had a huge, heavy, big-jawed head in proportion. They weren’t just casual visitors to the branch, either, but long-term residents raising the next generation inside the hollow as I proved by knocking the branch against a post and seeing eggs fall out:

ant and eggs
A worker from the first nest trying to rescue eggs

The ants in the second nest were much smaller, perhaps 10mm long, and prettier. They were also more agitated, moving so fast that it was almost impossible to get a photo.

silver-charcoal ants
Ants from the second nest

When one of them did stop to investigate a hole it bent forward in such a way as to show off its spiny body:

ant on branch
Investigating a hole

This spines are enough to identify it as a Polyrhachis species, but (as this page shows) we have well over 100 species in that genus in Australia and I haven’t tried to narrow it down.

To answer a couple of obvious questions …

  • My reminder about vacuums was ‘almost painful’ because I very nearly got bitten by soldiers of the first nest.
  • Carpenter bees also adopt frangipani hollows as nests (this one wasn’t smart enough but will give you the idea).
  • Our other ‘arboreal ants’ are the two species which make nests by sewing leaves together – Rattle Ants (another Polyrhachis species) and the very familiar Green-ants.

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