Army ant

Eciton_burchellii_army_ants

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Army ants, despite their small size, are deadly predators, and nothing can stand in their way, except, perhaps, a hungry anteater. These ants live in tropical climates in South America, Africa, and Asia. Army ants vary greatly in size from small workers, which can be only one tenth of an inch (3 mm), to the “soldiers,” which can grow up to one and one tenth inches (30 mm). The largest ant in the picture above is a soldier, and the other smaller ones are workers.

Raids

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In order to find their food, army ants go out on raids of up to 20 million individual ants. If all of the ants in one of these larger raids were combined, they could weigh over 200 pounds (90.7 kg). That’s more than most adult humans weigh! While on these massive raids, these ants can take down prey that is hundreds of times their size. This picture shows a swarm of army ants attacking a grasshopper that is many times their size. Besides eating grasshoppers, army ants also eat spiders, scorpions, other ants, lizards, and even small snakes and ground birds. Although army ants would not be able to attack and kill a human or large animal that is awake, they can give painful stings and bites. Click here to see a short video of an army ant raid. Sometimes army ants will climb trees in order to find prey. When they do this, it is very likely that they will come to a gap in trees or branches that may seem impossible for these mini marvels to cross. When this happens, these ants use strength in numbers to cross the gap.  These ants will make a living ant bridge to cross a gap. This trick will only work if the gap is small enough.

Benefits for other animals

Some birds, called ant birds, in the jungle where these ants live actually benefit from the ants raids. Instead of eating the ants, the birds will follow from a safe distance or from in trees and eat any insects they see fleeing from the oncoming hoard. Butterflies also benefit from army ants in a round-a-bout way. Instead of being interested in the ants or in the insects they catch, butterflies will sometimes feed on the ant birds’ droppings.

Life phases

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Army ants raid in a 35 day cycle that consists of two phases. The first stage lasts 20 days and is called the statary phase. During this time the colony will stay at a certain nest for the whole time, and the workers will only raid every few days. The queen army ant will also lay up to 100,000 eggs in this phase. By the time this phase is done, all of the eggs will have hatched into larva. For the next 15 days of the cycle, the army ants are in what is called the “nomadic phase.” During this time, because they have larva to feed, workers will go on a raid every day. The whole colony will also move to a new nest sight every night. One of the reasons the ants are able to move their nest every night is that their nest comes with them. This picture shows what army ant nest are made of: ants. At night, the worker ants group together to from a temporary nest where they can keep the queen and larva safe inside. After the “nomadic phase” is done, the cycle starts over.

Workers

There are four “groups” of workers in an army ant colony. The lowest two groups are called the “minims” and the “mediums.” These groups go out and attack prey. The ants in the next group, which is called the “sub-major” group, use their long legs to straddle prey. The largest group of workers includes ants known as “majors” that defend the colony from intruders. If any animal is unlucky enough to come across an army ant colony, the “majors” will use their huge jaws, called mandibles, to bite the intruder. They will also sting anything they see as a threat – including humans! The workers live up to one year before they die. All of these groups of worker ants are mostly blind, and they use scent and touch to find prey. Army ants can see a little bit but are only able to detect light and dark. Because of this, the best way for some insects to avoid being eaten is to stay completely still.

Fun fact

Army ant mandibles are so strong that some natives of South America use them as stitches on wounds. Doctors will allow the ants to bite the wound closed and will then kill the ant. The mandibles will stay shut, keeping the wound closed until it is healed.

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Photo credits:

  • Army ants: public domain
  • Army ants attacking grasshopper: Wikipedia user: Karmesinkoenig
  • Army ant temporary nest: Wikipedia user: Geoff Gallice
  • Mystery animal: Wikipedia user: Walterince
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