Episode 149 – Ants

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Listen to Episode 149 on PodBean, YouTube, Spotify, or wherever you listen to your favorite podcasts!

Incredibly diverse, eternally fascinating, and so ubiquitous today that it’s hard to imagine a world without them. This episode, we discuss the deep history of Ants.

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Small and Many

There are many ways to measure the “success” of a group of organisms. Often, biologists will consider a group successful if they are widespread across the globe, or if they maintain large populations, or if they feature a wide diversity of species. By those metrics, ants are remarkably, unbelievably successful. There are over 15,000 identified species of ants, and one study estimated the total number of ants on Earth to be approximately 20 quadrillion (that’s 20,000,000,000,000,000).

Ants belong to the insect group called Hymenoptera, which also includes bees and wasps. In terms of anatomy, ants can be identified by their uniquely elbowed antennae and their small “waist” featuring a structure called a petiole. And ants are famously social – eusocial, in fact; all ants live in colonies.

Here is a tiny fraction of modern ant diversity.
Top left: A bullet ant, Paraponera clavata. These ants are famous for their extremely painful stings. Image: Graham Wise, CC BY 2.0
Top right: Fire ants, also famous for their stings as well as their complex social coordination. Image: Stephen Ausmus, public domain
Bottom left: Dawn ants, also called dinosaur ants, Nothomyrmecia macrops. These ants exhibit a variety of possibly ancestral ant features. Image: CSIRO, CC BY 3.0
Bottom right: Two carpenter ants communicating. Image: NoahElhart, CC BY-SA 4.0
All over the world, ant colonies make use their numbers and their eusocial behavior to accomplish some extraordinary lifestyles.
Top left: Weaver ants build nests using the silk from their larvae. Image: Bernard DUPONT, CC BY-SA 2.0
Top right: Leafcutter ants harvest plants to feed gardens of fungus that provide food for the colony. Image: Pjt56, CC BY-SA 4.0
Bottom left: Fire ants use their bodies to create structures such as bridges and rafts. Image: Igor Chuxlancev, CC BY 4.0
Bottom right: Driver ants, a type of army ant, hunt and swarm larger animals. Image: Karmesinkoenig, CC BY-SA 2.0 DE
Ant colonies typically feature numerous castes of individuals genetically predisposed toward certain tasks and lifestyles, such as queens who lay eggs and soldiers who defend the colony. These castes can become quite extreme.
Top: Various castes of leafcutter ants. Image: GameKeeper, CC BY-SA 3.0
Bottom left: Honey ant colonies include workers who gorge themselves with food until they swell enormously. They then serve as living larders for other ants. Image: Greg Hume, CC BY 2.5
Bottom right: Some army ant soldiers have such large and powerful mandibles that they are unable to feed themselves. Workers place food in their mouths. Image: Alex Wild, CC0 1.0

Ancient Ants

Ants are small and delicate, but they are also numerous, and so the ant fossil record is quite rich. Hundreds of fossil ant species have been identified, including members of modern ant groups as well as totally extinct ant families. The oldest known ants are Cretaceous, over 100 million years old, and they already exhibit characteristics of eusociality. Even back during the Age of Dinosaurs, ants were ants.

Most fossil ants are either preserved within amber or as impressions in sediment.
Left: An ant inside Baltic amber. Amber tends to preserve ants that lived on or near trees. Image: Anders L. Damgaard, CC BY-SA 4.0
Right: Titanomyrma, a giant species of Eocene ant preserved in sediment. Image: Ute Kiel, CC BY 4.0
Other ant fossils include trace fossils such as ancient burrows or nests, and even one case of the “death grip” of a fungal-infected ant upon a leaf.
Haidomyrmecini are a group of extinct Cretaceous ants also known as “hell ants.”
These ants featured unique scythe-like mouthparts.
Top: Dhagnathos autokrator. Image: Vincent Perrichot, CC BY 4.0
Bottom: Haidomyrmex cerberus. Image: Vincent Perrichot, CC BY 4.0

There’s always more…

The abundance, biomass, and distribution of ants on Earth (and the study)

Evolution of the army ant syndrome (and the study)

The global expansion of the Argentine ant supercolony (technical, open access)

The rise of the ants (technical, open access)

Caste development and evolution in ants (technical, open access)

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