Soil Science

Ants

Meat ant dragging heavy gumnut.
Meat ant dragging heavy gumnut.

Take pity on this poor worker ant valiantly struggling back to the nest with its gumnut prize. Presumably to extract and eat the eucalyptus seeds. They have to forage quite a way from their nest so they have long legs and powerful jaws to hold and drag heavy things. Incredible claims are made about the weights ants can lift - anything up to 100 times their own body weight! Taking a conservative figure, ants can carry up to 5 times their own body weight in their mouths and can drag an object 25 times their weight.

One entrance to a meat ant nest. Here worker ants have decorated the top of the nest with gravel
One entrance to a meat ant nest.
Here worker ants have decorated the top of the nest with gravel

Ants are social insects living in colonies of many individuals. Each ant is assigned certain tasks within the colony according to its caste. The worker ant forages for food, builds and maintains the nest, and tends the queen ant, her eggs, larvae and pupae. If you pick up a rock covering an ants nest, a flurry of activity occurs as the workers scoop up the helpless white juvenile ants in their jaws and take them to safety deep within the nest.

Worker ants, under a rock, rescuing larva and pupal juvenile ants when disturbed.
Worker ants, under a rock, rescuing larva
and pupal juvenile ants when disturbed.

Worker ants are only one of several castes. Soldier castes defend the nest against maurauders with their large jaws (e.g. meat ants), stings (e.g. bulldog ants) or a formic acid spray from their hind end. There may be one or more queen ants per nest which lay all the eggs which produce the workers, soldiers and reproductive castes.

Bulldog ant nest guarded by soldier ant.
Bulldog ant nest guarded by soldier ant.

Ants feed on a great variety of things. Some bring dead leaves, twigs, dead and live insects and seeds back to the nest. They also feed on nectar. Some ants are omnivores, eating anything they can scavenge while others specialise solely in feeding on spider eggs, slaters or springtails using stings to subdue their prey. Some ants tend aphids and other insects in order to suck up the honeydew the aphids produce from their hind end.

Worker ants carrying dead beetle or cockroach back to nest (1/2)
Worker ants carrying dead beetle or cockroach back to nest (1/2)
Worker ants carrying dead beetle or cockroach back to nest
Worker ants carrying dead beetle or cockroach back to nest (2/2)

Ants nest in soil and wood. Nests in soil can range from simple chambers with a tiny entrance big enough for only one ant at a time, to the large and complex, gravel-covered mounds of meat ants with foraging runs radiating out many metres from the nest. Nests can house from 100 to a million ants.

Small ant nests, with 1 too many entrances. The lower nest has been excavated after rain into a tower-like entrance.
Small ant nests, with 1 too many entrances. The lower nest has been excavated after rain into a tower-like entrance. (1/3)
Small ant nests, with 1 too many entrances. The lower nest has been excavated after rain into a tower-like entrance.
Small ant nests, with 1 too many entrances. The lower nest has been excavated after rain into a tower-like entrance. (2/3)
Small ant nests, with 1 too many entrances. The lower nest has been excavated after rain into a tower-like entrance.
Small ant nests, with 1 too many entrances. The lower nest has been excavated after rain into a tower-like entrance. (3/3)

The meat ant mounds pictured below had many entrances and when disturbed by this photographer, ants swarmed out of the entrance, attacking her sandal-shod feet with their jaws. Luckily meat ants don't have stings! Galleries in meat ant nests can be 2 m deep. Some ant nests have a raised entrance on a tower-like structure. Ants nesting in wood build far simpler nests.

Large meat ant nest with many enterances.
Large meat ant nest with many enterances.

Ants in your plants! In open woodlands of northern Queensland ants live inside plants. The "ant plant" has a swollen base with hollows in it, rather like the galleries of an ant's nest. Ants invade the stem and make themselves at home. The plant benefits by absorbing nutrients from the discarded food and waste of the ant colony.

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