A hole near home plate leads to inspection of ant colony
There is an open field not far from my house in town that Parks and Rec keeps mowed. About the size of a city block, it is home to a small picnic shelter, a basketball court, some playground equipment, 14 trees and an overgrown ballfield.
On our morning walk the other day, the brown dog and I ambled up to the pitcher’s “mound,” really just a rectangular pad of white rubber on the flat acre of the unloved diamond. The infield was so covered in weeds and clumps of grass that, had I not known the basepaths by heart, I couldn’t have walked the circuit, touching all the bases that were miraculously still in place.
By the pitching rubber and again near home plate were a couple of cleat holes suggesting someone might have been there, perhaps working on their curveball and slider.
From the time I was in third grade through junior high, baseball was essentially the reason for summer. Little League ball was wonderful, with players chattering at every position and everyone wearing a T-shirt with the team’s logo.But organized ball was just a couple times a week. The rest of the time you’d make do with whomever showed up at the small field by the elementary school, or just hit grounders, liners and fungoes to your buddy or kid brother in the backyard.
The concept of a weeded-over ballfield was unimaginable back in the day.
Now, about those cleat holes. If you’re wearing cleats, you’ll leave a lot more than two or three pokes in dry ground. A closer inspection found a little halo of dirt crumbs surrounding one of the holes, which might make a myrmecologist — an ant biologist — think of Formica incerta, a ⅕-inch-long ant with the hard-to-beat moniker of the “uncertain field ant.”
I’ve not found a convincing explanation for what it’s uncertain about, but it is one of the most commonly found species in recently restored grasslands, which I suppose is one way to think of an abandoned ballfield. And it is a species that doesn’t create a conical mound of soil particles at the entrance to its nest.
Although I didn’t see any ants at that hole, nearby was another opening with a stream of exceedingly small (about 1/16 inch), yellowish brown ants coursing back and forth to a clump of grass a few inches away.
I’m guessing they might have been “thief ants” (Solenopsis molesta), so called because of their habit of nesting near to and stealing food and larvae from neighboring ant colonies. But without collecting a few specimens to study under a microscope and a good reference, these off-the-cuff IDs of my two diamond ants are likely enough well off the mark.
There are more than 22,000 species of ants
There are a lot of species of ants; almost 22,000 have been identified so far. So rather than trying to pick our way through a lesson on some of their basic biology, let’s just toss out a random scattering of observations provided by our friends, the myrmecologists.
A careful study published in 2022 conservatively estimated the number of all ants in the world to be around 20 quadrillion — that’s 20 thousand million million individuals — comprising a total mass topping that of all birds and wild mammals combined.
It’s well known that in most species, only the queens can mate with the males (who are only produced during the short period for reproduction). However, I was surprised to learn that many species have multiple queens in their colonies, while a few others have no queen at all. In these last, the workers (all of whom are female) reproduce asexually, cloning genetically identical copies of themselves.
The typical species of ant lives in a single colony (which may have multiple entrances) and will kill individuals of the same species from other colonies that try to enter. However, more than 150 species are known to create multiple, unconnected colonies, with workers carrying food and larvae freely between nests.
Supercolonies live in Argentina
The invasive Argentine ant, Linepithema humile, takes this behavior to an extreme. Within a given geographical area, members of neighboring colonies freely intermix, forming supercolonies that can extend for incredible distances.
The aptly named Very Large Colony of coastal California extends some 560 miles from San Diego to north of San Francisco and is estimated to have a population of nearly one trillion individuals.
However, that’s peanuts compared to a supercolony in southern Europe that stretches more than 3,700 miles from Italy along the Mediterranean to the Atlantic coast of Spain. But the Argentines’ tolerance of other members of its own species does not extend to other species of ants.
The International Union for Conservation of Nature has named the Argentine ant one of the world’s 100 worst invasive species due to its aggressive displacement of native ants and the many negative impacts that has on indigenous ecosystems.
Ken Baker is a retired professor of biology and environmental studies. If you have a natural history topic you would like Baker to consider for a column, email your idea to [email protected].
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