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