Attaantium

Kelly’s Field Notes

Common Name: Leafcutter ants

Order: Hymenoptera

Family: Formicidae

Tribe: Attini

Genus: Atta, Acromyrmex, Amoimyrmex

Species Near You: There are around 55 species of leafcutter ant.

• Texas leafcutter ant (Atta texana) - found throughout Texas and parts of Louisiana

• Leafcutter ant (Atta sexdens) - common in Central America and northern South America

Description: 

Leafcutter ants range in size from about 1 mm (minims) to over 15 mm (soldiers). Leafcutter ant queens are the largest members of the colony (Richardson et al., 2022). In Atta species (the larger of the three genera), queens can reach about 20–30 mm (about 1 to 1.2 inches) in length, making them among the largest ants in the world. Leafcutter ants are reddish-brown, with strong serrated mandibles. 

Leafcutter ants have been farming Lepiotaceae fungi for 50 million years; they are arguably our oldest farmers. Leafcutter ants bring pieces of leaves back to their colony which they are incapable of digesting. Instead, they rely on cultivating Lepiotaceae fungus to break down the leaves, making them nutritionally available to the ants (Tsang, 2017). This relationship is found in over 250 species of ants (not all leafcutters), all found in the Americas. The other ants are a sub-group of Attini that gather fallen leaves, debris, and insect carcasses to start their gardens. Without the fungi the ant colony will die as it is their only source of food. But this relationship is not one-sided! Like many of the crops humans have cultivated over time, the ants’ fungus is found nowhere else in the wild. The queens take fungus with them in a specialized pouch in their mouths (infrabuccal pocket) on their mating flights to start a new colony.

Colony Life:

Leafcutter ant colonies are organized into a caste system consisting of four roles: Queen, Soldier, Worker, Minim. The queen is the reproductive role, laying all of the eggs. She's also the longest lived, with some surviving up to 20 years. One colony can have multiple queens (Richardson et al., 2022)!

The soldiers (also called majors) are the defense force of the colony. They have large heads which hold equally as large mandibles. The soldiers’ mandibles are so specialized they cannot feed themselves. They rely on workers to exchange food from their mouths into the soldier’s mouth. This behavior is called trophallaxis. In some cultures the mandibles of soldier leafcutter ants were used as sutures by forcing the ant to bite then removing its head, leaving it stuck with jaws closed on the wound (Davis, 2019). Soldiers have a measured bite force of 1,029 mN (1 Newton) which is 2,600 times their body weight (Püffel et al., 2023). While Dr. Justin O. Schmidt didn’t have any leafcutter ants in his book The Sting of the Wild as he mostly covers venomous bites not mechanical bites, other people who have been bitten by leafcutter ant soldiers have expressed the bite is painful but not long lasting — probably similar to being cut with a small blade.

Workers (also called mediae or minors) venture out of the nest to forage for leaves to cut. They have specialized serrated mandibles made to cut the leaves into manageable pieces. Workers come in several sizes which dictate what the workers bring back to the nest. Smaller workers with shorter mandibles cut and carry leaves, while larger workers with longer mandibles cut up fruit pieces for smaller workers to carry (Helanterä and Ratnieks, 2008). The serrated mandibles of workers are reinforced with zinc, which keeps the mandibles sharp despite their frequent use (Schofield et al., 2002). You will often find long lines of workers with minims riding on their freshly cut leaves. The minims fight off phorid flies trying to lay parasitic eggs on the back of otherwise occupied workers. 

Minims are also the fungal gardeners of the colony. They chew up leaves, adding the pulp to the final garden as nutrient sources. Leafcutter ants do not eat the leaves, they eat the fungus that eats the leaves! They also weed the garden, removing any undesirable fungi, bacteria, or molds. Minims have salivary glands that secrete several different types of antibiotics, which act as a fungicide, killing undesirable fungi (Schoenian et al., 2011).  They also carry antibiotic-producing Actinobacteria species on their underbellies, which looks like powdered sugar. But their job doesn't stop there! Minims are also the colony’s care givers and garbage women. They tend to eggs and larvae, feeding larvae, keeping them clean, and at optimal temperatures. They also remove any waste from the gardens and the colony in general, moving it to a dedicated waste area. 

In addition to using pheromones, leafcutter ants communicate via stridulation, by rubbing parts of their abdomens together. Workers will stridulate any time they are prevented from moving freely. For example, if part of a nest is caved in the trapped workers will stridulate, summoning other workers to dig them out. Interestingly, they do not respond to airborne stridulation, only vibrational signals sent through soil (Roces et al., 1993).

Leafcutter ants colonies can get very large! Some colonies are as deep as 6 meters (20 ft) and cover more than 372 m2 (4,000 ft2). Additionally there is never just one entrance to a colony. Colonies can have hundreds of different entrance points. The tunnels connecting the entrances and colony chambers can be as long as 488 meters (1,600 ft) (Richardson et al., 2022).

Cockroach Symbiosis:

Some leafcutter ants allow ant cockroaches (Attaphila spp.) to live among them, feeding on their fungus gardens and the lipids that form on the outside of the ant’s cuticle. The ant cockroaches emit an odor that smells like the leafcutter ants allowing them to live without harassment among their ant hosts. To find a colony they either hitch a ride on incoming leaves or they follow an ant pheromone trail back to the nest. In order to disperse they take a ride on virgin queens leaving the colony on their mating flight.  There are currently nine described species of cockroach ant that live with leafcutter ants (Bohn et al., 2021).

Super Powers:

• Soldier jaws - soldiers bite with a force 2,600 times greater than their body weight! If a 185 lb human could bite with 2,600 times their body weight the bite force would be 481,000 lbs of force. Roughly the weight of 160 full-sized pickup trucks coming through their jaws.

• Worker jaws - the serrated mandibles of workers are reinforced with zinc among the proteins in their teeth, which keeps them sharp. Workers use a scissor motion to cut leaves and fruit.

• Antibiotics - minims secrete antibiotics from their salivary glands to keep undesirable fungi at bay within their colonies. They also carry antibiotic-producing Actinobacteria species on their underbellies, which looks like powdered sugar. This rubs onto their fungus gardens as they walk through it.

• Strength - leafcutter ants can carry objects over 50 times their own body weight (Painter, 2016)!

• Friends - one ant colony can have millions of members (Painter, 2016)! They also have cockroaches that live with them, but that relationship is less mutualistic than their relationship with the fungus. 

• Stridulation - workers can rub parts of their abdomens together to signal for help when trapped.

• Gardening - minims maintain a fungus garden that feeds the entire colony

• Sutures - leafcutter ant soldiers can be used to close wounds by forcing the ant to bite then removing its head.

• Many sizes - multiple castes for specialized jobs and division of labor. All of them are metaphorical queens.

References:

Bohn, Horst, et al. "Revision of the genus Attaphila (Blattodea: Blaberoidea), myrmecophiles living in the mushroom gardens of leaf-cutting ants." Arthropod systematics & phylogeny 79 (2021): 205-280.

Davis, Hillary E. "Leaf-cutter ants in wound closure." Wilderness & Environmental Medicine 30.4 (2019): 469-470.

Helanterä, Heikki, and Francis LW Ratnieks. "Geometry explains the benefits of division of labour in a leafcutter ant." Proceedings of the Royal Society B: Biological Sciences 275.1640 (2008): 1255-1260.

Painter, Betsy. “5 Fascinating Facts about Leaf Cutter Ants.” U.S. Fish & Wildlife Service, 2016, www.fws.gov/story/2016-03/5-fascinating-facts-about-leaf-cutter-ants.

‌Püffel, Frederik, Flavio Roces, and David Labonte. "Strong positive allometry of bite force in leaf-cutter ants increases the range of cuttable plant tissues." Journal of Experimental Biology 226.13 (2023): jeb245140.

Richardson, Steven, et al. “Atta Texana, Texas Leaf Cutter Ant (Hymenoptera: Formicidae).” LSU Ag Center, (2022) www.lsuagcenter.com/articles/page1649168993168. Accessed 20 Mar. 2026.

Roces, Flavio, J. Tautz, and Bert Hölldobler. "Stridulation in leaf-cutting ants." Naturwissenschaften 80.11 (1993): 521-524.

Schoenian, Ilka, et al. "Chemical basis of the synergism and antagonism in microbial communities in the nests of leaf-cutting ants." Proceedings of the National Academy of Sciences 108.5 (2011): 1955-1960.

Schofield, Robert MS, Michael H. Nesson, and Kathleen A. Richardson. "Tooth hardness increases with zinc-content in mandibles of young adult leaf-cutter ants." Naturwissenschaften 89.12 (2002): 579-583.

Tsang, Jennifer. “The Leaf-Cutter Ant’s 50 Million Years of Farming.” ASM.org, 26 Sept. 2017, asm.org/Articles/2017/September/the-leaf-cutter-ant-s-50-million-years-of-farming.