When Ants Squeak.Eavesdropping Secretly gaining unauthorized access to confidential communications. Examples include listening to radio transmissions or using laser interferometers to reconstitute conversations by reflecting laser beams off windows that are vibrating in synchrony to the sound in the room. on lesser-known Bulletins from the hill
If you haven't stuck an ant in your ear recently, don't write the insect off as the strong, silent type.
Many species make tiny squeaks that people can hear if they hold an ant close enough. The rich chemical communication of ants has claimed more attention from scientists in recent decades, but a small band of researchers has been sorting out ant sounds.
Biologists have long realized that ants can hear with their knees, picking up vibrations humming through leaves or nests or even the ground. In the past 20 years, researchers interpreting the messages that thrum thrum 1
v. thrummed, thrum·ming, thrums
1. Music To play (a stringed instrument) idly or monotonously: thrummed a guitar.
2. in substrates have revealed a sort of ant-ernet, zinging with communiques about lost relatives, great food, free rides for hitchhikers, caterpillars in search of ant partners, and impending im·pend
intr.v. im·pend·ed, im·pend·ing, im·pends
1. To be about to occur: Her retirement is impending.
2. doom. Improvements in recording equipment are expanding the range of ant chirps and buzzes available to human eavesdroppers. Some scientists are even challenging decades of textbook truths and suggesting that ants might also be able to detect certain kinds of airborne sounds.
For almost a century, naturalists have considered ants practically deaf to sounds traveling through the air but exquisitely responsive to vibrations. The noises that ants seem to make intentionally, drummings and fast stridulatory strid·u·late
v. strid·u·lat·ed, strid·u·lat·ing, strid·u·lates
To produce a shrill grating, chirping, or hissing sound by rubbing body parts together, as certain insects do.
v.tr. scrapings of roughened rough·en
tr. & intr.v. rough·ened, rough·en·ing, rough·ens
To make or become rough.
Adj. 1. roughened - used of skin roughened as a result of cold or exposure; "chapped lips"
chapped, cracked body parts, can buzz through substrates easily.
Drumming, also called body rapping, turns up most often in species with wood or dried-pulp nests. For example, when a carpenter ant nest gets disturbed, workers rock furiously back and forth so their mandibles in front and their hindmost hind·most also hind·er·most
Farthest to the rear; last.
furthest back; last
Adj. 1. body part wham against the nest. An ant pounds the nest in a burst, up to seven thumps at 50-millisecond intervals.
The other obvious ant sound, the squeak that people can sometimes detect, comes from stridulation stridulation
creation of a sound by rubbing two parts of the body together, e.g. cicada. . This high-pitched rasping rasp
v. rasped, rasp·ing, rasps
1. To file or scrape with a coarse file having sharp projections.
2. To utter in a grating voice.
3. of one surface against another occurs frequently in animals, most famously among cicadas, katydids, and crickets but also catfish and, some scientists argue, sea horses.
Ants stridulate strid·u·late
v. strid·u·lat·ed, strid·u·lat·ing, strid·u·lates
To produce a shrill grating, chirping, or hissing sound by rubbing body parts together, as certain insects do.
v.tr. with the hindmost body section, the gaster gaster /gas·ter/ (gas´ter) [Gr.] stomach.
[Gr.] see stomach. , explains systematist Philip Ward at the University of California, Davis The University of California, Davis, commonly known as UC Davis, is one of the ten campuses of the University of California, and was established as the University Farm in 1905. . The gaster is made up of segments, one of which bears a ridged patch. Its nearest neighbor sports a file-like rasping widget Pronounced "wih-jit," for decades, the term has been a popular word for a generic "thing" when there is no real name for it. It is often used to describe examples of made-up products along with other fictitious names; for example, "10 widgets, 5 frabbits and 2 dingits. . The segments remind Ward of the nested tubes of a telescope. "Imagine the meeting edges scratching a bit as they move in and out," he says.
Residents of the southwestern United States can hear stridulatory concerts by picking up red desert ants, suggests Ward. In the Northeast, the less common but hefty Myrmica species also squeak audibly when plucked up by a human hand.
Ants in four subfamilies stridulate, but others seem silent and don't have recognizable scraping surfaces, Ward notes. Entomologists The following is a list of entomologists, people who have studied insects.
Name Born Died Country Speciality
John Abbot 1751 1840 United States argue about whether this pattern means stridulation evolved several times in ants or whether the Adam and Eve Adam and Eve
In the Judeo-Christian and Islamic traditions, the parents of the human race. Genesis gives two versions of their creation. In the first, God creates “male and female in his own image” on the sixth day. of ant ancestors rasped to each other but some descendants lost the ability.
In the 1970s, pioneering studies of these ant scratchings showed that they boosted the listening ants' response to the pheromone pheromone
Any chemical compound secreted by an organism in minute amounts to elicit a particular reaction from other organisms of the same species. Pheromones are widespread among insects and vertebrates (except birds) and are present in some fungi, slime molds, and algae. signals indicating that dinner or a nest site is available.
Stridulation also seems to summon rescuers after a nest cave-in. Hubert Markl of the University of Konstanz The University of Konstanz (German: Universität Konstanz) is a university in the city of Konstanz in Baden-Württemberg, Germany. It was founded in 1966, and the main campus on the Gießberg was opened in 1972. in Germany reported that leaf-cutter workers converged at a spot where nestmates were trapped 5 centimeters down in well-packed soil. If the workers were buried only 3 cm below ground, nestmates not only milled around the spot but dug toward the pinned ants.
Stridulation can also signal "stop already" from a female Pogonomyrmex whose sperm-storage organ can't hold any more. Ants don't make this stridulation during the earlier courtship, Markl reports, and the distinctive sound benefits both sexes by reducing time- and energy-wasting activity.
One of the more unusual notions about stridulation arose in 1995 when Flavio Roces and Bert Holldobler of the University of Wurzburg in Germany reported that leaf-cutting ants tend to stridulate as they slice off snippets of tender leaves. The vibrations make their jaws buzz as they rip through plant tissue (SN: 11/26/94, p. 358). Could ants have evolved the electric knife?
However, offering ants both prime leaves and chemically tainted ones revealed that workers stridulate more on desirable than less-favored leaves, regardless of any differences in the toughness of the cutting task.
Buzzing jaws do make smoother cuts, the researchers found, but don't improve speed or efficiency. The scientists now look to communication instead of cutting enhancement as the driving force behind the evolution of ant humming. "The electric knife is a wonderful epiphenomenon epiphenomenon /epi·phe·nom·e·non/ (ep?i-fe-nom´e-non) an accessory, exceptional, or accidental occurrence in the course of any disease.
n. ," as Holldobler puts it, sounding a little wistful.
The same line of research on leaf-cutter stridulation revealed a related function: an invitation to hitchhikers. When the ants forage, the smallest workers, or minims, swarm along even though they're too little to do any cutting. They scurry around the cutting site or stand nearby with mandibles open and antennae outstretched out·stretch
tr.v. out·stretched, out·stretch·ing, out·stretch·es
To stretch out; extend.
Adjective . Many don't walk back to the nest on their own but literally hitchhike hitch·hike
v. hitch·hiked, hitch·hik·ing, hitch·hikes
To travel by soliciting free rides along a road.
To solicit or get (a free ride) along a road. on the loads carried by the bigger ants.
Despite the appearance of frivolous gawking, the little hitchhikers provide a useful service. Somehow, they discourage attacks from phorid flies. These parasites swoop onto leaf-cutters and inject an egg, which hatches and chews through the ant's innards, finishing with the brain and leaving a headless corpse.
Roces and Holldobler noted that cutters stridulate extrafast when they come to the end of their task and heave the leaf fragment into carrying position. When the researchers artificially vibrated a leaf, it attracted more hitchhikers than a leaf without an experimental buzz. The scientists suggest that the tiny bodyguards find their rides by listening for the stridulation.
Ants listen for more than the buzz of their own kind, as Phil DeVries of the University of Oregon The University of Oregon is a public university located in Eugene, Oregon. The university was founded in 1876, graduating its first class two years later. The University of Oregon is one of 60 members of the Association of American Universities. in Eugene shows with his singing caterpillars. The larvae Larvae, in Roman religion
Larvae: see lemures. of many species of two butterfly groups, lycaenids and riodinids, sport glands that ooze a sweet liquid of interest to ants. As the ants collect the bounty, they discourage attacks from the caterpillars' predators.
DeVries found that caterpillars advertise their delicious presence with vibrations that ants can detect along quivering plant stems and leaves. He's recorded a considerable variety of these caterpillar calls, ranging from a sound, he says, like "bub ... bub ..." to fancier noises such as "beep ah ah ah beep" and "biddup ... biddup ... biddup."
DeVries has also investigated whether caterpillars can fake ant sounds. The Maculinea butterflies would have good reason to do so, he reasons. Very young caterpillars topple off food plants. They lie there wiggling and making noises until picked up by roving ants. Perhaps a little dim about taxonomy, the ants bring a fallen caterpillar back to their nest and tuck it into the brood chamber. They don't seem to object as the newcomer eats some of the young ants that are its nurserymates.
When the caterpillar finally matures, two ant species recognize their mistake and kill the freeloader free·load
intr.v. free·load·ed, free·load·ing, free·loads Slang
To take advantage of the charity, generosity, or hospitality of others. , but a third ant leaves it unharmed. For the caterpillar, "there's strong selection to attract the right ant."
When DeVries compared the sounds made by the caterpillars and ants, he found that despite their overall differences, "some components of the caterpillar calls were dead on."
People don't do anywhere as well as caterpillars in communicating with ants. Shouting at an ant is a bit like shouting at a computer or a cat. You may not see any sign that you've been heard.
"Ants don't respond to sound on a human scale," says Robert Hickling of the National Center for Physical Acoustics at the University of Mississippi The University of Mississippi, also known as Ole Miss, is a public, coeducational research university located in Oxford, Mississippi. Founded in 1848, the school is composed of the main campus in Oxford and three branch campuses located in Booneville, Tupelo, and Southaven. in Oxford. That quirk, he argues, has hobbled the study of ant acoustics for a century.
Ants may not pick sounds of stridulations out of the air as people do, but--in theory at least--ants may respond to airborne vibrations if scientists make the right noise.
"It all started with the sensor," remembers Peng Lee, an acoustical and electrical engineer who works with Hickling. In the mid-1990s Lee was struggling to make a device sensitive enough to detect the dreaded pink bollworm pink bollworm, destructive larva of a moth, Pectinophora gossypiella. Probably of Native American origin, it is a serious pest of cotton in the S United States, chiefly along the Mexican border. just by listening for the sounds of larvae munching.
His early version succeeded miserably well. In a field test on an Israeli kibbutz kibbutz: see collective farm.
Israeli communal settlement in which all wealth is held in common and profits are reinvested in the settlement. The first kibbutz was founded in Palestine in 1909; most have since been agricultural. , the device picked up so many faraway tractors and planes that the technological din drowned out any bollworms.
As Lee tinkered with the oversensitive o·ver·sen·si·tive
Extremely or excessively sensitive.
over·sen gizmo Slang for any hardware device. See gadget. back in Mississippi, lab conversation drifted to speculation on whether fire ants make noises and what they'd sound like if they did.
Two decades earlier, researchers in the laboratory of Walter R. Tschinkel of Florida State University Florida State University, at Tallahassee; coeducational; chartered 1851, opened 1857. Present name was adopted in 1947. Special research facilities include those in nuclear science and oceanography. in Tallahassee had used less elaborate equipment to try to capture sounds from the imported black fire ant and others in the genus Solenopsis. The experiment yielded scratchy sounds from one of the black fire ant's larger relatives, but the invader itself revealed nothing that the scientists could record.
Lee and Hickling took their new sensor out to the nearest mound of black fire ants and poked in the probe. "There was a big uproar," Hickling says. "You could hear individual ants as they passed by the microphone."
In other experiments, the team collected the noise of some important episodes in ant life. For instance, the scientists provided a caterpillar and eavesdropped on its demise. With such a sensitive acoustic view, they recorded more than the ants' sounds. "You could hear the caterpillar struggling," Hickling says. "I felt sorry for it."
They also recorded two colonies clashing. The thumps and thuds of activity, however, drowned out any stridulations from the contending armies. "The sound of the struggle tended to be quite loud," Hickling notes. Lee adds another tribulation: "I got stung a lot."
The researchers also brought a fire ant indoors, but the recording session did not turn out to be easy. They didn't know how to cue the ant to make noises. After hours of experimentation, one of Lee's colleagues discovered that attaching a weight to the ant's antenna provoked a recordable sound.
A debut selection of black fire ant recordings are available at a special ant sound Web site, http://home.olemiss. edu/~hickling. The site has already attracted a query from a Hollywood screenwriter, Lee notes.
Picking a relatively tranquil moment for the fire ant mound, the researchers played back recordings of the pandemonium in the colony. "I was expecting them to get all upset," Hickling recounts. However, the colony showed no sign of a response. "I had to backtrack somewhat," Lee understates.
Other scientists have interpreted ants' apparent lack of response to sounds that interest humans as an inability to hear vibrations in the air. Hickling and Lee have come up with another possibility. Ants might hear only what acousticians call "near-field sound."
A tiny source like an ant that makes long sound waves creates a special effect in the first few centimeters of the emission, Hickling explains. Such nearfield sound decays not as the inverse of distance from the source but as the inverse of distance squared. An ant might respond only to this kind of sound, he suggests.
"It's not easy to test," Hickling points out. To create that special-effects zone, the sound source has to be minute compared with the wavelength. Broadcasting sounds from standard speakers, even ones a few inches tall, won't work to study this kind of hearing.
Hickling and Lee are trying to make an ant-size sound source. They've started with a source that stands a few inches high and is shielded so that sound blares only from the front. They added a long funnel that compresses the sound waves and guides them to a pinhole opening. They described the project at the annual meeting of the Entomological Society of America The Entomological Society of America (ESA) was founded in 1889 and today has more than 6,000 members, including educators, extension personnel, consultants, students, researchers, and scientists from agricultural departments, health agencies, private industries, colleges and in Atlanta in December 1999.
Holldobler notes that, so far, there's no behavioral evidence of airborne sound reception by the ants. He says, "There is a possibility that ants perceive near-field sound, or wind velocity produced by the sound wave, as has been shown for honey bees, but the work is preliminary as far as I can judge it."
The idea of ants perceiving near-field sound strikes Tschinkel as "plausible." In the tight spaces inside a nest, such close-range communication might prove useful because chemical communication can be difficult to modulate at close range. The possibility of near-field-sound communication interests Tschinkel because, he says, "it could fill a gap."
Acoustic studies might eventually also fill a gap in fire ant control, Hickling daydreams. "You can't just put a rock band over their mound and they'd go away--bioacoustics doesn't work like that," he acknowledges, adding, "I'm not sure whether I'd rather have a rock band in my yard than fire ants."
In either case, shouting won't help.