Pheidole is one of the most diverse ant genera in the world, with 1,004 currently described species. This genus is known for having two worker castes – a “minor” and a “major”. The major caste typically sports a head that is comically larger than minor heads. You can see why Pheidole species are called the “big-headed ants”:

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Two majors and a minor of Pheidole xerophila. Photo: Alex Wild

This ant group provides an excellent study system for investigating a fundamental question in ant research: How, and why, do major and minor worker castes evolve? Dr. Jo-anne Holley and colleagues addressed just this question in a study published earlier this year.

Regular readers of The Daily Ant likely already know that ants are very good at most things. From farming to construction to warfare, ants are rivaled perhaps only by humans. So, it is not surprising that along with a diverse array of interesting and intriguing behaviors, ants are also excellent at something we humans find a little less exciting: biological invasions.

This is a turtle:turtle

Many people around the world believe that turtles are boring.

This is a turtle ant:

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Photo: Alex Wild

Many people around the world believe that turtle ants are fascinating.

Reportedly, one of the turtle ant characteristics that people love most is how they use their heads to block their nest entrances. But these turtle ants may also provide insights into the evolution of worker castes in ants, as shown recently by Dr. Robert Planqué and colleagues in a new study published in the Journal of Evolutionary Biology.

Ant researchers have long known that ants swap food and enzymes orally through a process called “trophallaxis” (tro-fuh-lax-is). Ants use a special organ, the crop, as a kind of “social stomach” – many workers eat food only to regurgitate it into larvae. But a recent study has found that this ant spit may serve another critical purpose: communication.

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If this ant wants to talk to you, it will spit in your mouth. Photo: Alex Wild

In an exciting new study recently available online in the journal Animal Behaviour, researchers found that two species of ants are selective in their use of tools for liquid food transport. Although tool use in ants has already established in previous studies, the mechanisms involved in tool use selection have rarely been investigated. Dr. István Maák and colleagues found that ants exhibit selective behavior in tool use, preferring materials that exhibit optimal handling and/or soaking properties. Perhaps most intriguing, the ants learned to preferentially use artificial tools that have superior properties for liquid food transport when compared to tools in their natural environment.

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Aphaenogaster ants feed on a seed food body. Photo credit: Alex Wild

Several human societies adopt nomadic lifestyles. From Yugurs on the Asian steppe to the Beja in northern Africa, these cultures traditionally gather food by tracking changing resources rather than relying solely on stable but geographically restricted food production. Not to be outdone by humans, some ants also exhibit nomadic behavior, most famously the army ants. But in 2008, Volker Witte and Ulrich Maschwitz reported an extraordinary and previously unknown behavior in ants: mushroom harvesting nomadism.

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