Columnist antsy about
bugs
Wild Williamsburg probes the lives of those social, marching
ants
By Callan Bentley
Flat Hat Variety Editor
A little over two years ago I received a fabulous gift. It was my father who bestowed this treasure upon me, a reward for graduating high school. Two days after being presented with my diploma, I was on a jetliner bound for the most ancient of continents, Australia.
My father and brother accompanied me Down Under, and we spend three grand weeks touring the Reef, the rainforest, and the Outback. The wildlife there fired my imagination.
Once, on a hike through a mangrove swamp, we came across a strange amalgamation of leaves hanging from a tree. The fronds appeared to have been glues together with a white substance. The structure was ovoid in shape. It was a little bit larger than a football (an American football, mind you; Australian footballs are enormous).
Being curious naturalists, we naturally started poking at it with a stick. Immediately hundreds of emerald green ants poured out of a hole near the bottom. They swarmed all over the hive, looking for their attacker. We dropped the stick and took a healthy step back. The little insects looked vicious, and we didn't want them casting their antennae in our direction. Sure enough, a few days later, both my father and brother were bitten by green ants when we stumbled across another nest.
While there are no green ants in Williamsburg, there are many other varieties, and they merit some consideration here. Ants are social insects, and like the bees and wasps, they are grouped together in the order Hymenoptera. Many people equate termites with ants, but these actually fall into another order, the Isoptera. Perhaps we will encounter them in Wild Williamsburg another week.
Many insects group themselves together in large bunches. Gnat swarms are one annoying example of this, while immense congregations of monarch butterflies migrating south are a more pleasant manifestation of the phenomenon. The difference between these insects and the ants (and bees), however, is that if an individual ant gets separated from the rest of its group, it will die. As Sue Hubbell points out in her book Broadsides from the Other Orders, it's much like human society: "Members of the colony become specialized in one or another of life's problems - getting food, nurturing larvae, defending the colony, or reproducing, for example - and in many cases, one set of specialists… is incapable of doing the job of others." Like millions of sex-legged musketeers, it's all for one and one for all in the ant world. E pluribus unum.
An interesting example of this arises in the area of food collection. While ants are well known for their ability to lift objects many times their own weight, they often need assistance for really big food items, which must be divided up into smaller pieces. When an ant finds a piece of food too large for it to carry alone, it heads back towards the anthill, pressing its abdomen to the ground every few centimeters, and leave a small amount of pheromone there. This creates a scent trail that other ants from the colony will follow to the food source, marching in something like single file. I was once hiking in the College Woods when I heard a soft crackling sound. I stopped to better listen, and looked down to discover that one of these "ant lines" was crossing the trail directly in front of me. There were so many ants marching there that the collective sound of their footsteps was actually audible!
As there were many ants that day in the College Woods, there are many ants across the globe. Some estimates put ants down as composing as much as a quarter of the earth's biomass. According to a November 1989 article in the journal Science, ants outweigh vertebrates in the Brazilian Amazon by a factor of four to one.
With a population that high, there's bound to be a lot of variation among the different groups of ants. Leaf-cutter ants, for example, have developed quite an interesting method of food gathering. These ants have evolved special scissor-like jaws, which they use to clip off pieces of green leaves. They do not eat these leaf bits, but take them to a large "growing chamber" where the leaves serve as sustenance for a fungus. The fungus is cultivated by the ants, and harvested to feed the colony.
Honeypot ants employ a different tactic. Some of these ants suck on roots and accumulate sugars for their entire lives. In the process, the abdomens of the honeypot ants become grotesquely swollen, eventually gaining the appearance of a grape. They are, in essence, living storage pots, full of syrup. When another ant gets hungry, it goes over to the honeypot and requests a meal, which the honeypot then happily regurgitates.
Sara Stein mentions a different feeding modification in her excellent publication The Evolution Book. By stroking the hindparts of an aphid with its feelers, an ant can induce the aphid to exude a drop of honeydew. This is a waste product as far as the aphid is concerned, and it emerges from the anus. To the ant, it's food, and is chugged faster than a fraternity boy shotgunning a Budweiser.
Another interesting modification is found in a group of ants that dwell in tree trunks. The entrance to their colony is a small hole. A certain group of ants within the colony have developed specialized heads, shaped like bottle corks, which they use to plug the entrance. Ants returning to the colony must tap a special code with their antennae on the guard ant's head. If they do not tap the proper code, the guard ant will not retract its head, ant the outside ant will not gain entrance to the colony.
The truly amazing thing about
ants (and all insects) is that there are so many of them out there, and that
there are so few known to science. This means even more incredible adaptations
likely exist out there somewhere. Who knows what other amazing ants Mother Nature
has dreamed up?