Honey, there are ants in my kitchen again! Just look at them!” The anguished wail from my wife brings me running from my study. Sure enough, an occasional ant hurries along the countertop, around the sink, and over the edge, meeting, stopping, and touching antennae with another ant going the other way before continuing on, eventually vanishing into a pinprick hole between the tile and the baseboard. There aren’t a lot of them. But my wife’s kitchen is her domain, and to her the only good ant is a dead ant. She has no tolerance for those tinuy biblical teachers of wisdom scurrying through her kitchen.
But for her biologist husband, her invitation to “just look at them” is a welcome opportunity for an experiment. So, on my belly on the tile floor, I watch in wonder as the ants hurry back and forth along an invisible trail. Wetting my finger with my tongue, I wipe it across the trail as if it were a grease pencil mark. A few seconds later the next little traveler along the trail runs into my invisible swipe as if it were a block wall. It stops, turns around, and runs back to where it came from as if checking to see if it was on the right trail. Then it returns to the swiped area and halts. Ants approaching the other side of the swipe do the same thing. In moments, ants on the both side of the gap mill around in confusion, just a half inch apart from each other. They get bolder in hteir casting round for the trail. Soon they are on it again, rapidly establishing an invisible detour around an invisible gap.
The invisible trail is, for the ants with their excellent chemical detecting antennae, a very real trail of pheromones. The ants I am watching must be trail marking with their abdomen, because I don’t see them doing anyhting else but running. Using a bit of detergenton a kitchen sponge, I can wipe out great lengths of the trail – that really confuses the poor ants. But when I come back in an hour they have reestablished an alternative route.
By now my sweetheart has had enough of the experiments and wants the ants out of her kitchen. Time to move into exterminating mode.