In John Muir’s My First Summer in the Sierra, published in 1911, he writes: “…one is almost tempted at times to regard a small savage black ant as the master existence of this vast mountain world.” Other names he refers to ants as are “fierce creatures” and “fearless, restless, wandering imps.” It might seem a little harsh to describe such a diminutive insect as “savage” and “fierce,” until you learn that they are, or can be, brutally vicious creatures.

Little did I know the day I was watching an army of golden ants cross my brick patio that the white cylinder logs they were carrying was pupae — immature ants encased in cocoons. I also didn’t realize that the stolen goods would emerge as slaves to their captors. Neil Tsutsui, a professor in the department of environmental science, policy, and management at UC Berkeley, describes the raid. “The slave-making ants (Polyergus mexicanus or Western Amazon ant) are in the midst of kidnapping babies from their host species, most likely field ants (Formica spp.), and transporting them back to a life of slavery in the Polyergus colony.”

Fascinating! But before slave raiding starts, an entire cycle of setting up a new kingdom — or, should I say, queendom — takes place.

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“A virgin Western Amazon ant queen attracts males from nearby Western Amazon ant colonies (using pheromones), they mate, and then the newly mated queen goes inside the field ant colony, kills the queen, and becomes accepted by the field ant workers as the new queen,” Tsutsui said. The field ants begin their task of taking care of the queen’s Amazon eggs. “The adult Western Amazon ants then start conducting raids on nearby field ant colonies to replenish their slave population.”   

UC Davis graduate student Matthew Prebus is researching the taxonomy, molecular phylogeny, and biogeography of ants. He explained the raiding process. First, Western Amazon ants send out scouts early in the day and once a field ant’s nest is located in their vicinity they lay a chemical trail between the nests, which the raiding column of Western Amazon ants follows. They then steal the field ant pupae, bring them back to their nest, and after the “kidnapped” field ants emerge they “perform the quotidian tasks in the nest, such as foraging for food for the Western Amazon ants and raising their young.”

Professor Philip Ward from the entomology and nematology department at UC Davis says a Western Amazon ant colony will raid multiple field ant nests over a season. As for the food and feeding process, he adds that adult ants consume liquids only, honeydew (liquid secretions from aphids, scales, etc.), and insect hemolymph (blood), the field ant regurgitating the food into the mouths of the Western Amazon ant.

It’s curious that field ants don’t refuse their new subservient role. “Basically, whatever they [field ants] experience or are exposed to when they first emerge, that is what they assume is ‘home’ and ‘family,’” said Candice Torres, a former graduate student of Tsutsui’s.  

Bottom line: Western Amazon ant workers can’t survive without field ant slaves.

Since Western Amazon ants inhabit a variety of environments — conifer and broadleaf woodlands, pinyon juniper, and cold desert shrublands, fields, parks, gardens, and prairies — there is great opportunity to witness the raids, which take place on hot afternoons in July or August; otherwise, they are rarely seen.

While ants may be clandestine in their work, there’s a whole lot of them around. It’s been estimated that the total weight of ants on earth outweighs the total weight of humans (it’s a matter of debate in the scientific field, but how can we really count the ants or weigh all humans?). That little ant you dismiss as you walk down the trail isn’t the harmless little guy we might have thought it was; it is widespread, and demonstrating that slavery in the insect world is very much alive.

~ Do you have a question about our region’s environment? Email editors@moonshineink.com.

Author

  • Eve Quesnel

    Eve Quesnel has lived in Truckee for 35 years with her husband Bill, once-upon-a-time daughter Kim-now on her own-and many dogs through the years, currently a Border Collie-Aussi mix. Her favorite pastimes include walking in her neighborhood and nearby woods, hiking in the high Sierra, and reading and writing. Quesnel is now retired from teaching English at Sierra College in Truckee but continues to pursue several writing projects. She is intrigued by the natural world of which she explores and writes about for the column "Nature's Corner" in Moonshine Ink.

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