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Spec Tech: Talking to Insects

October 21, 2010

I enjoyed Chris Doty’s August 26 blog on Linguistic Quirkiness. In that spirit, and coming from my own biological bent, I’d like to consider some zoological approaches to communication. No, I’m not going to interrogate the whole animal world here, but restrict myself to just a couple of insects. I want to consider how insects communicate and how we humans have, after decoding these ‘languages’, used them to communicate with the insects themselves. Ever since I was a kid I’ve found such communication intriguing, I think in large part because insects are truly alien to us and the methods employed for insect communication suggest some of the alternative ways that extraterrestrials might use to communicate. And also raise the hope that we humans can, perhaps, communicate with aliens.

Talking to Ants

There is something about ants that I have always found fascinating. Maybe it’s their articulated bodies that remind me of tiny robots, almost as if I could build one myself with tweezers, a magnifying lens, and a set of mail-order parts from Lilliputia. Maybe it’s their sheer numbers: not just one tiny robot, but dozens, hundreds, thousands! A swarming army of tiny robots.

But when it comes to communication they use nothing like the beeping, inflectionless speech we typically associate with robots.

Ants use many methods of communication, including tiny chirpings, but the method with which we humans are most familiar is the use of pheromones. By ‘pheromones’ I mean the production of secreted chemicals that stimulate specific responses in other members of the colony. Pheromones are thought to be the chief means of communication among ants and are perceived (smelled) with their antennae. There are several things that make such pheromones a great communication system when you are an ant. First, they are effective in the dark, such as underground. Second, they can operate even when you are not around, like leaving a note for a friend. Third, they are extremely efficient, the antenna of ants being able to sense only a few molecules of some pheromones.

The most commonly known of the pheromones are those involved in recruitment, such as in the pheromone trails that ants leave to lead other ants to food. The ants keep leaving the pheromone trail as long as the food supply exists, but when the food supply is used up they stop leaving the trail and the scent evaporates, the trail left by a single ant disappearing within a matter of minutes. It is not, however, an all or nothing proposition: ants leave varying amounts of the pheromone depending on the quality and quantity of the food. In addition, so that other ants will know that they are being recruited to a food source, rather than say to fight enemies, ants may regurgitate contents from their crop when they meet up with another ant.

But such recruitment pheromones are just the tip of the iceberg. Chemical signals are also used to identify the colony and the castes within the colony, to induce grooming, clustering, and digging, to raise an alarm, and to induce the removal of dead ants. Queens produce additional pheromones, for instance those involved in attracting workers to the queen; when the queens stop producing a pheromone, workers then know it is time to raise a new queen. There are even such things as ‘propaganda’ pheromones used by several different species of slave-making ants. These ants raid other ant colonies to take slaves and, when doing so, secrete a pheromone that alarms and disperses the defenders, in some cases even inducing the defenders to fight among themselves.

How do ants produce their pheromones, the elements that make up their language? Well, they have many mouths, so to speak. To be more specific, they have glands scattered throughout their bodies, from head to anus, dedicated to the production of different chemicals. And it’s not just that each gland produces a single chemical. As a general rule they produce blends of chemicals. Different blends may allow an ant to recognize whether a signal originates from an ant of its own colony or species. Different blends may also allow for greater information content in a pheromone message.

And yes, from what we have already learned, humans can now speak to ants in their own language.

Or course, given our relationship with ants, this communication is generally not beneficial to the ants. The pheromone produced by queens to attract the worker ants can be used as an attractant for ant traps. The chemical oleic acid is released by ant corpses as a breakdown product and is sufficient to induce other ants to remove the corpse the nest. As a result, oleic acid has been used by researchers for what can charitably be described as a ‘practical joke’. If a small amount of oleic acid is daubed on a living ant, the other ants assume that it is dead, pick it up, and carry it away from the next for disposal. The bespattered ants will attempt to clean themselves off and return to the nest, but if any scent remains their comrades will grab them once again and unceremoniously take them back to the trash heap.

Really, when you think about it, in their stereotyped responses to a communication signal, ants seem quite robot-like even when it comes to language.

Talking to Bees

Ah bees! Bees! I do love them and feel a dark pain for the troubles that have beset them the past few decades, with honey bee populations decimated by mite infestations in the 1990’s and more recently by colony collapse disorder. Now I am always on the lookout for honeybees, searching for signs of their rejuvenation. On sunny days I’ll stand beside the clematis vine that engulfs the fence outside our house, producing thousands of small white flowers in the autumn, and there I’ll listen to the comforting buzz of the pollinators and count the proportion of bumble to honey bees, giving a silent cheer for each honey bee I discover.

Part of my love for honeybees comes from them having one of the most ingenious methods of communication found in any animal: the waggle dance. It’s been known at least since the early 1800’s that bees dance, but it wasn’t until the studies of Karl von Frisch in the mid-twentieth century that these movements were deciphered as a form of language, one that bees use to give information about direction, distance, and quality of food to their nest-mates. A worker bee having discovered a food source will return to the nest and perform a waggle dance on the vertical honeycomb for the edification of the other bees.

The waggle dance takes the form of a figure-eight pattern: there is a straight run during which the bee waggles its backside back and forth, following which the bee will turn either right or left and run around in a circle back to its starting point to repeat the waggle phase of the dance once again. The direction and duration of the waggle runs correlate with direction and distance to the food source. Directions are given with reference to the position of the sun. If the food source is in line with the sun then the waggle run will be vertical on the comb, and any angle to the left or right of the sun will be described by a corresponding angle away from the vertical. Distance is based on the number of waggles during the waggle run. In addition, by their level of excitement the worker bees can give an indication of the quality of the food source. I love the ritualistic elements of the dance language, the sense that the bee is a hunter returning to its tribe and retelling the epic tale of a search for food through mime and dance and that, inspired by example, the hunter’s comrades then leave home to take up a similar quest.

There’s more to the waggle dance than just these bare essentials, enough to keep bee researchers busy and debating for a good half-century now and still counting. For instance, by attaching tiny harmonic responders to bees, radar has been used to follow the flight-paths of individual bees, the results supporting the idea that recruited bees fly to the vicinity of the source, and then locate the exact location through odor and other cues. There’s also the question as to how bees describe distance. It turns out that the amount of time spent waggling does not correspond to an exact distance measurement (e.g. 75 milliseconds of the waggle dance corresponding to 100 meters). Rather distance is described in terms of the level of visual stimuli along the path to the food source, similarly to how we might tell someone to drive past ten telephone poles to get to a location, regardless of the spacing between the telephone poles. Also, if a dead bee is placed at the food source, then returning bees are less likely to perform a waggle dance, presumably because the dead bee suggests a predator is lurking nearby.

Do we know enough of this bee language to talk to bees?

Yes!

Scientists have done so, and the coolest part of this is that they have used robot bees—yes tiny robots!—to talk to the real live bees. Wolfgang Kirchner and Axel Michelson, later joined by other colleagues, designed a motorized bee made of brass, coated with wax, and with wings fashioned from razor blades. Simply dancing was not enough to convince the honeybees that the robot was telling them anything significant. But when the robot vibrated its wings to produce the acoustic signature of a real bee, and when the robot dispensed a drop of sugar solution to let the bees know the robot was describing a food source, then the bees followed the flight path described by the robot.

Recommended Reading:

1. THE ANTS, by Bert Holldobler and Edward O. Wilson. The Bible of the ant field, beautifully illustrated and enjoyable by scientist and non-scientist alike.

2. “Trailhead,” by Edward O. Wilson. A short story recently published in the New Yorker exploring how the death of a queen affects an ant colony, and which reads like a piece of science fiction about an alien species.

3. “Stardance,” by Spider and Jeanne Robinson. The Hugo- and Nebula-winning novella that became the seed for three novels. I remember reading Stardance when it first came out in Analog and then later seeing a photo of Spider Robinson, a skinny guy with really long hair and a crazy grin, and thinking just what a hippy that guy was. Stardance with the idea that dance can be a universal language of communication just seemed to fit right in with that image, just the sort of thing a hippy would write. But, really, what’s wrong with that, I’d like to know.

4. “Depressed by a Book of Bad Poetry, I Walk Toward an Unused Pasture and Invite the Insects to Join Me,” by James Wright. A wonderful piece of whimsy from one of my favorite poets.

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