Australian spider ants are elegant little machines
Bec Crew is a Sydney-based science communicator with a love for weird and wonderful animals. From strange behaviours and special adaptations to newly discovered species and the researchers who find them, her topics celebrate how alien yet relatable so many of the creatures that live amongst us can be.
Superficially, they look like tiny spiders, which is where their common name, spider ants, comes from.
Almost all spider-ant species hail from our neck of the woods (eastern Australia, New Caledonia, New Guinea and parts of Indonesia), except for one: Leptomyrmex relictus, which somehow made its way to central Brazil.
These ants have been unofficially split into two groups. The macro-Leptomyrmex are relatively large, and can come in black, orange or black and orange varieties, like our little friend above, photographed in the Oxley Wild Rivers National Park in Yarrowitch, New South Wales.
Then there are the micro-Leptomyrmex species, all of which have been discovered recently, and all of which come from the rainforests of southeast Australia.
Colony life for spider ants is complex, fascinating, and, honestly, a little creepy.
The colonies are usually made up of a few hundred worker ants and a single queen, who in most Leptomyrmex species is wingless. This is unusual, because in many other ant species, the queen is easily distinguished from her subjects by having the marks of wings she shed after having dispersed from her birth colony.
Another odd aspect of Leptomyrmex life is the fact that they relegate certain worker ants to the status of ‘repletes’, which are basically living Tupperware containers.
All ants, regardless of species have two stomachs. One stomach is their own personal stomach, which they use to nourish themselves. The other is the ‘social stomach’, used to nourish their colony-mates. Ants can regurgitate food into the mouths of their peers like bird mothers do for their chicks.
Spider ants take this social feeding one step further by designating certain ants as walking social stomachs. Their only job is to store water and nutrients, which can be essential to the survival of the colony during times of drought.
Repletes are designated from a very young age – they never have a chance to forage out in the open like the worker ants.
Instead, when their bodies are still forming and therefore soft and malleable, the worker ants will start transferring food and water into their mouths, filling them up so much that their stomachs (within the gaster, or the back part of the ant) distend dramatically.
The repletes will live inside the nest for their whole lives, waiting for worker ants to take nutrients from them, or to fill them back up from the spoils of their foraging trip.
And, weirdly enough, these ants have taken to hanging from the ceiling of their nest, like tiny bats, as you can see in this fascinating video about them:
When foraging, spider ants usually go out alone or in groups of two or three, so be careful not to tread on one when you’re in their space.
Be sure to keep your eyes well-peeled when trekking though forest and mountainous areas with high rainfall in eastern Australia – you just might spot one going about its important business.