This week my son and I have been watching a toothbrush. No, we haven’t gone bonkers. This does have something to do with ants.
You see, we saw this post about an unusual Ant-traction. It seems that a certain type of ant likes the rubbery buttons Colgate toothbrushes. Go check it out. Here’s a link to the original post, as well.
The first thing we wondered, of course, was whether this is a prank or hoax. I think you could get the same effect by rubbing a little sugar water or honey on the brush.
We bought a toothbrush to check it out. So far our fire ants, Solenopsis xyloni, could care less about the toothbrush. But that doesn’t mean the effect isn’t real. It could be that the rubbery bit contains a pheromone specific to one or a few closely-related species of ants. We are going to continue our experiments.
If there turns out to be something to this, it won’t be the first time humans have inadvertently produced a product that mimics an insect pheromone. One classic example is the finding that termites of the species Reticulotermes flavipes will follow an ink trail drawn by a certain type of pen. (See for example, this experiment).
If you’d like to learn more, here is a video showing EO Wilson explaining some of the basics of pheromones and other chemical signals in ants:
We’ll let you know if we get any ants to react.
And please let us know if you try this experiment, what your results were, and what kinds of ants you used.
I’ve just been reading a book on katydids, which are insects renowned for their ability to sing. What about ants? Are they the strong silent types?
It turns out that ants can make plenty of music. They can squeak, drum and rattle as well. There is nothing quiet about ants. As Dr. Francesca Barbero of the University of Turin says, “Sound in information exchange within ant colonies has been greatly underestimated.”
Ants with underground nests occasionally get buried when a tunnel collapses. Scientists have shown trapped ants of certain species can make sounds by rubbing sections of their rear section or gaster together. On one segment of the gaster there is a patch of tiny ridges like a file. On the petiole is a curved ridge called a scraper. The ant produces a squeaking sound when she rubs them together, which known as stridulation. You can produce a sound in a similar way by rubbing a craft stick across a comb. When other workers detect the sound, they rush to help dig out the trapped ant(s).
Researchers have been able to record sounds from individual ants. The sounds are in the audible range for humans and can be heard distinctly when amplified. Listen to the sounds of a fire ant stridulating at Stridulation Sounds of Black Fire Ants by Dr. Robert Hickling. (The link is broken, so I found some more recordings -later post).
Stridulation has other functions as well. Male and female harvester ants sing to one another as they take off on their mating flights. Mated females also stridulate to signal to pursuing males that they are no longer interested. In other species, foragers may stridulate when they find food to attract help, although they often release pheromones as well.
Leafcutter ants are known to stridulate while cutting pieces of leaf. It appears the noise the cutting ants make attracts other ants to come take the pieces of leaf to carry them back to the nest. Some ant scientists have suggested that the vibrations improve the ants’ ability to cut smoothly through the leaf. Leafcutter ants also produce sounds while building their nests in the soil.
Example video of Acromyrmex ant stridulating
Some other insect species associated with ants also stridulate to attract the ants’ attention. The caterpillars of the beautiful Imperial blue butterfly have “teeth” on their abdomen, which they scrape against a series of grooves to produce grunts and hisses. They can also make a drumming sound. All these different calls seem to be used for different situations, but not all the details are clear yet. What is known is when scientists glued up the noise-producing organs with shellac, the ants took longer to find the caterpillars and spent less time with them than with the ones who had not been silenced.
As I mentioned in the post about blue butterflies, Rebel’s large blue (Maculinea rebeli) larvae have recently been shown to mimic the sounds produced by the queen ants of their hosts to elicit food, care and even rescues, at the expense of the colony’s own offspring. Go to “Caterpillar noise tricks ants into service” article at Science News to actually hear the sounds the caterpillars and ants make. Edit: Hear the audio links here at Science.
I studied carpenter ants, and whenever I opened a nest, I could hear the ants react. The workers strike their mandibles and gasters on the surface of the tunnels in their wooden nest to create a drumming sound. Ants deeper in the nest rush to the site of the disturbance and assist their sisters with defending the nest.
The rattle ants of Australia also tap their gasters when they encounter an enemy intruder, such as a bird feasting on their nestmates. They live in leaf nests high in trees. The leaves may be slightly dry and the tapping produces an audible rattling sound that gives these ants their name.
Rattan ants of Asia live in thorny rattan vines. When an intruder gets too near their nest the ants hit their mandibles against the stem of the plant. Because they hit in a synchronized way, the sound pulses. (I was interested to learn that some katydids also drum or vibrate the plants, especially species that stay hidden deep in foliage. )
Where are the ants’ ears? No one knows for absolutely sure how it all works. Some ants have ways to detect surface vibrations in their legs. It is also likely that certain ants use hair-like sensors in the tips of their antennae. When the hairs are displaced the ants detect signals that are called nearfield. Those are signals from sources that are extremely close. The ants remain completely unaware of sounds produced by far objects, like us shouting at them for example.
In any case, as our human sound equipment becomes refined, I’m sure we will be hearing more from ants.
Bug Bytes, the USDA Sound library of Richard Mankin, has a number of ant recordings.
Barbero, F., J.A. Thomas, S. Bonelli, E. Balletto, and K. Schönrogge. 2009. Queen Ants Make Distinctive Sounds That Are Mimicked by a Butterfly Social Parasite. Science 323 (5915) 782.
Donato A. Grasso, Marco Priano, Gianni Pavan, Alessandra Mori, Francesco Le Moli. 2000. Stridulation in four species of Messor ants (Hymenoptera, Formicidae). Italian Journal of Zoology, Volume 67, Issue 3: 281 – 283
Have you heard the buzz about the fungus-gardening ant, Mycocepurus smithii? Apparently the queens can crank out workers and new queens without fertilization of the eggs. Genetic studies have shown the workers to be clones of their queen mother. No males have ever been found in nature, and laboratory colonies can’t be induced to make males either. Although in haplodiploid species males are usually generated without fertilization, this may be the first case of female ants being produced this way.
Parthenogenesis is the development of individuals from an egg that has not been fertilized. Although more commonly known from aphids, a number of species of Hymenoptera are parthenogenetic as well. Recent studies have shown in some of these cases the absence of males is due to infection by a bacteria, such as Wolbachia. The ant researchers indicate that bacterial infection isn’t the case in Mycocepurus smithii.
The consequences of asexual reproduction in these fungus-gardening ants are still under debate. Scientist Anna Himler has already suggested that there is a link between the ants and the fungus that grows in their gardens, because the fungus also reproduces asexually. We will probably hear more as these ants will certainly be given closer scrutiny.
After posting photographs of butterflies last week, I decided to take a deeper look into the relationships between ants and blue butterflies. There’s been a lot of new discoveries in this area over the last decade or so.
Butterflies of the family Lycaenidae, commonly referred to as blues, hairstreaks and coppers, have been known to have a variety of fascinating relationships with ants. Most caterpillars of lycaenid butterflies feed on leaves, flowers and seeds of their host plants. They also have specialized glands that make a sweet liquid. The ants are attracted to the glands and feed on the secretions just like they do with the honeydew of aphids or scale insects. In return the ants protect the caterpillars, or at least as best they can.
For example, the endangered Karner blue butterfly, Lycaeides melissa, caterpillars feed on lupines. The caterpillars have three glands that produce a mixture of carbohydrates and amino acids. Eleven species of ants have been recorded visiting the caterpillars, and larvae tended by ants have been shown to have higher survival, presumably due to lower predation.
In New South Wales, Australia, the very rare Bathurst copper (Paralucia spinifera) caterpillars also produce sweet rewards for the ants. In exchange, the ants take extra good care of them. The ants are like goatherds, keeping the caterpillars like miniature goats. At night the ants herd the caterpillars up into the bushes where the caterpillars feed on the plants. In the morning the ants herd them back down into the ants’ nest where the caterpillars rest for the day. The next night, out they go again. In fact, if someone starts to disturb the caterpillars while they are out feeding, half the ants attack the intruder while the rest round up the caterpillars and head them back down to the nest.
Imperial blue butterfly caterpillars (Jalmenus evagoras) of Australia have been found to “call’ to their ant attendants by stridulating. Researchers have found that the larvae produce three different types of calls. Both the larvae and the pupae have single-celled glands over their bodies that produce attractants. In this case the ants guard both the larvae and the pupae of the butterfly.
In this video you can see the glands of the caterpillar.
Ant-Caterpillar mutualism video
A few caterpillars have even more glands that release substances to appease and fool the ants even more. The caterpillar of a dainty alcon blue butterfly (Maculinea alcon) from Denmark uses its glands to fool foraging worker ants into taking it back to their nest. Once inside, the caterpillar kills and eats ant larvae while the guard ants rest calmly nearby. In fact the ants actually mistake the pink-colored caterpillar for one of their own larvae, and give it food and care. Eventually the caterpillar transforms into a pupa, but still remains underground under the protection of the ants. Only once it emerges as an adult butterfly do the ants recognize it as an enemy and attack it, so the butterfly must quickly exit the anthill before it is discovered.
Finally, the Rebel’s large blue, Maculinea rebeli, has taken deception to the maximum. The larvae have recently been shown to mimic the sounds produced by the queen ants of their hosts to elicit food, care and even rescues, at the expense of the colony’s own offspring. Go to “Caterpillar noise tricks ants into service” article at Science News to actually hear the sounds the caterpillars and ants make. Now, that’s interesting.
Darlyne A. Murawski. (2003). Killer caterpillars: built to eat flesh. National Geographic. June. pp. 100-111.
Francesca Barbero, Jeremy A Thomas, Simona Bonelli, Emilio Balletto, Karsten Schönrogge. Queen Ants Make Distinctive Sounds That Are Mimicked by a Butterfly Social Parasite. Science. 6 February 2009:
Vol. 323. no. 5915, pp. 782 – 785.
P. J. DeVries. Enhancement of Symbioses Between Butterfly Caterpillars and Ants by Vibrational Communication Science. 1 June 1990: Vol. 248. no. 4959, pp. 1104 – 1106.
In this book, Chapter 18 has extensive information about the Imperial blue.