Army ants

Army ants are just as intense as they sound. They are the Mongol hordes of the ant world. They are relentless, brutal and I love them. They can hunt all the insects in a particular area of rain forest that they need to move to new areas. They build living bridges, homes out of their own bodies and eat almost anything they come in contact with. They’re absolutely mental so buckle up.

There are over 200 species of army ants and they are known by many different names including Legionary ants and Driver ants. They are found on all continents except Antarctica with even a few species existing on the fringes of Europe. Still find it weird that the only place that doesn’t have ants is called ANTarctica. For legal reasons I must say that this is a joke and I know why it is called Antarctica. We will focus on 4 of the 17 genera of army ants today because I do not expect you to sit through such a long post.

Army ants distribution (Alex White).

The first we will cover is Eciton as it is one of the most famous and recognisable genera of Army ants. They are from central and south America and are among the most studied and understood army ants in the world. They form massive colonies with millions of individuals. Their soldiers are some of the strangest looking and most recognisable ants in the world.

An Eciton burchellii soldier (Alex Wild).

They eat everything in their path including arthropods, birds and even snakes! Army ants are nomadic, frequently moving around as they hunt so many insects, their territory can run out of food for them! Digging a nest takes forever and is hard work. There is no need to do this if the colony only stays in 1 place for less than a month. So they build their nests out of their bodies. These are called bivouacs.

Eciton burchellii bivouac.

Maquipucuna reserve, Pichincha, Ecuador
The surface of an army ant bivouac made of the ants themselves, Eciton burchellii (Alex Wild).

Driver ants are old world army ants that live across Africa and Asia. They are very diverse and exploit so many niches. The larger Dorylus species are much less subtle. These large ladies just cut their way through the forests. They create trails because walking over things just takes too much time. Colonies can exceed 20,000,000 ants. These ants do bother to build temporary nests as they would rather have their work force hunting everything that moves.

Dorylus sp. soldier guarding a nearby column (Alex White).

They eat everything. I’m talking birds, insects, snakes and even Mammals. Up to half a million insects a day. They eat so much that the forests literally run out of food for them. So, they are nomadic, moving around finding more food and eventually the colonies will have to split in two just so they can find enough food. They are so successful that they have evolved self limiting mechanisms. That is mental. The Queens of the largest species are also known to be the largest ants in the world reaching 5 or even 8 centimetres sometimes. A little bit insane but still very cool.

Dorylus helvolus
Dorlylus helvolus workers and soldiers (Alex Wild).

Dorylus helvolus is a beautiful red species of driver ant. Similar species are mostly subterranean to keep safe and hidden from predators and prey alike. They eat a whole host of insects including moths. Some of the smaller species are even known to feed on other ants and their young. Kind of rude but kind of understandable. Free food and they clearly aren’t a fan of kids!

Labidus coecus
Labidus coecus showing off her formidable jaws.

Labidus is a genus which contains fewer species than the others we talked about. They have a far more generalised diet. They will eat things such as fruit, seeds, nuts and even rice as well as their meat-based diet. Their bivouacs occur underground in rotten logs or in abandoned Ant nests. Although they only have a few species, they are packed into their environment with several species overlapping. The colonies contain up to a million individuals and they mostly forage underground. Because they are subterranean, we don’t know much about these ants. We do know that the attack other Ant colonies but know nothing about their reproduction. So, if you feel like you are the one to figure out more about these ants please have a go. They forage in swarms like all other army ants and eat most things they encounter.

Aenictus laeviceps
A Worker of Aenictus laeviceps (Alex Wild)

Aenictus are an old-world genus of army ants. They mostly feed on social insects including other ants. They have been seen eating other insects, but this is unusual behaviour for them. Nests contain up to 80,000 ants. We just don’t know a lot about them which means more people need to study ants! They hunt underground, above ground and even in trees eating any ants, wasps or termites they find! As with many species of army ant, Aenictus have no eyes! They feel and smell their way around. Seeing as there are so many species of army ant, it clearly works for them. They are an uncommon ant genus that are difficult to find. This makes them difficult to study which is why they are very mysterious in scientific works.

We understand so much about army ants but there is so much that we still don’t know. Some species are only known from a single ant! We need to study them as much as possible both now and in future generations.

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References

Baudier, K.M., D’Amelio, C.L., Sulger, E., O’Connor, M.P. and O’Donnell, S., 2019. Plastic collective endothermy in a complex animal society (army ant bivouacs: Eciton burchellii parvispinum). Ecography42(4), pp.730-739.

Berghoff, S.M., Maschwitz, U. and Linsenmair, K.E., 2003. Influence of the hypogaeic army ant Dorylus (Dichthadia) laevigatus on tropical arthropod communities. Oecologia135(1), pp.149-157.

Berghoff, S.M., Weissflog, A., Linsenmair, K.E., Mohamed, M. and Maschwitz, U., 2002. Nesting habits and colony composition of the hypogaeic army ant Dorylus (Dichthadia) laevigatus Fr. Smith. Insectes sociaux49(4), pp.380-387.

Binghaniri, A., 1993. The army ant genus Aenictus (Hymenoptera: Formicidae) from Thailand and Viet Nam, with descriptions of three new species. Bull. Biogeogr. Soc. Japan48(2), pp.68-72.

Borowiec, M.L., 2016. Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae). ZooKeys, (608), p.1.

Fowler, H.G., 1979. Notes on Labidus praedator (Fr. Smith) in Paraguay (Hymenoptera: Formicidae: Dorylinae: Ecitonini). Journal of Natural History13(1), pp.3-10.

Gotwald Jr, W.H., 1995. Army ants: the biology of social predation. Cornell University Press.

Monteiro, A.F., Sujii, E.R. and Morais, H.C., 2008. Chemically based interactions and nutritional ecology of Labidus praedator (Formicidae: Ecitoninae) in an agroecosystem adjacent to a gallery forest. Revista Brasileira de Zoologia25(4), pp.674-681.

Perfecto, I., 1992. Observations of a Labidus coecus (Latreille) underground raid in the central highlands of Costa Rica. Psyche99(2-3), pp.214-220.

Vosseler, J., 1905. Die ostafrikanische Treiberameise (Siafu). Der Pflanzer1, pp.289-302.

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