Trap-jaw ants are the venus fly traps of ants, in the tropical/subtropical genus Odontomachus. They are some of the most incredible animals on earth, because of the speed at which they can snap their jaws together to snatch their prey. The species at left, O. clarus, is one I encountered in Arizona. Like many desert animals, these ants like to hunt at night, and it was common to see them milling about on the University of Arizona campus in the glow of the street lights. The workers are striking to see because they walk about with their huge jaws in the open position. In the picture you can barely see tiny trigger hairs, which are similar to trigger hairs in venus fly traps. Because this is an animal, though, there are large jaw muscles which contract like coiled springs to hold the jaws open. When there is pressure on a trigger hair, the effect is like unhooking a latch (think of a mousetrap), and the jaws explosively close on their prey, at a nearly unimaginable speed:

"Biologists clocked the speed at which the trap-jaw ant, Odontomachus bauri [at right], closes its mandibles at 35 to 64 meters per second, or 78 to 145 miles per hour - an action they say is the fastest self-powered predatory strike in the animal kingdom. The average duration of a strike was a mere 0.13 milliseconds, or 2,300 times faster than the blink of an eye."

To record the entire motion requires filming the ants at 50,000 frames per second, rather than the usual 24.

In their paper published last August (Patek, S.N., J.E. Baio, B.L. Fisher, and A.V. Suarez, 2006. Multifunctionality and mechanical origins: Ballistic jaw propulsion in trap-jaw ants. Proceedings of the National Academy of Sciences 103: 12787-12792), researchers added to this incredible story by discovering an additional purpose of the trap jaws. They first calculated the force of the mandibles: "...a single mandible could potentially generate a force that is 371-504 times the ant's body weight." Then they documented a previously unknown use for this force in O. bauri: self-propulsion.

You must watch these videos to fully appreciate this behavior. But, to summarize, by snapping their jaws against a hard surface, O. bauri achieves "heights up to 8.3 centimeters and horizontal distances up to 39.6 centimeters. That roughly translates, for a 5-foot-6-inch tall human, into a height of 44 feet and a horizontal distance of 132 feet." Of course, whenever comparisons are made between insects and humans, the former come out looking like Schwarzeneggers to the hundredth power. This is because such comparisons do not take into account the effects of scaling. The insect world, with the same gravity and atmosphere as we have, but with exoskeletons and light weight, is a very different place (which is a topic for a later time). Everyone knows you can drop an insect from great height and it will emerge unscathed. This is very useful if your escape route is flying eight times your body length straight up into the air.

To see some amazing biodiversity in action, watch the videos.


More incredible ant pictures are posted at myrmecos.net!

Labels: ants, behavior, biodiversity, cool bugs, ecology, insects

I decided a good weekly column would be a post about one of the cool insects I have known during my career.

My first featured bug will be a species of honeypot ant from the southwestern deserts, Myrmecocystus mexicanus.

This is a fun species to mess with because they are the most nocturnal ants I've ever seen. Some other species are nocturnal, but you sometimes see them during the day; others you find at night but they can be easily observed with a flashlight. M. mexicanus, however, is completely anti-phototaxic - the second a light is shone on workers, they run away from it. This provides a cool effect when you go out at night an locate a nest, which is very distinctive. When you shine a flashlight on the nest, you see a lot of ants hanging around on the surface that immediately go down the hole, as if they were being slowly sucked. Turn off the light a minute, then turn it back on, and you can repeat the process. Kinda mean to do over and over, I guess, but this is serious minutes of entertainment.

I got to know these ants while working as a field assistant on a grad student's project. The grad and I mused that it would be great fun to design different types of ant furniture, including an M. mexicanus lamp. The colony could be contained in a hollow lamp, which they could crawl around on but not off (there are handy materials for keeping ants contained). When you turned on the light at night, they would all quietly slip back into the lamp, which would then be ant-free in a couple seconds. Hmm, maybe not a huge money-maker, but it could definitely be marketed to entomologists...

The cool thing about honeypot ants in general (i.e., several species in the genus Myrmecocystus) is that they use some workers, called replete workers, as storage vessels. This is a great way to get through the dry season in a desert. They in turn become famine food for larger animals, including humans - the abdomens are quite sweet and tasty. Some people with captive colonies feed the ants specific foods to get a good flavor in the replete workers. Molasses is supposed to be a good one.

There are several more pictures of the M. mexicanus here.

Labels: ants, biodiversity, cool bugs, ecology, insects

Anyone who cared to peruse the links to the left around the Biotunes site would know that I have a particular fondness of ants. In fact, I consider them to be the pinnacle of evolution. Yep, newsflash for all you "evolution-must-mean-progress- because-look-at-humans" types out there - humans ain't at the tip.

Why are ants so ubiquitous and speciose, and probably found in more habitats on earth than any other family of organisms? (I made up that last part but it could easily be true - anyone out there know?) One good guess is eusociality. Most animal species are solitary, but some are social. There are several different levels of sociality, but the most evolutionarily derived form is eusociality, which means there is a complete division of labor among individuals in a colony. Henry Ford had it right - the most efficient way to produce something is through specialization of tasks necessary to reach the goal. In ants, the queen's only job is to lay eggs. The workers specialize on various tasks such as nest cleaning, larva rearing, foraging and protection of the nest. Many humans like to fool themselves that they are good multitaskers, but our brains say otherwise. Even we are more efficient when we focus on one task. But we aren't as efficient at producing more humans as ants are at producing more ants.


Although humans are not eusocial, we are social, and a lot of what we do is going to be affected by the basic biological need to fit in socially - no man is an island.
What is interesting to me is that we are in a current fad in which everyone wants to use gender as a construct to explain general social behavior. Probably that's because we seem to have hit a brick ceiling in terms of women's progress in various professions, and there seem to be a lot of people dying to explain it in terms of gender genetics (e.g., the infamous Larry Summers). But what if all these beloved "differences" between men and women were explained by sociality?

In every species, solitary and social, males and females obviously have different reproductive roles. But societies are more complex. In many mammal societies there are alpha (reproductive) males and females with other individuals filling other roles. Humans are even less social than that, because generally everyone has the chance to reproduce. Also in general, those that conform to cultural norms are more likely to reproduce. (Hence my argument in the last post that any genes associated with autism are likely to be spreading, because many people who do not conform to societal norms have found a way to make a pile of money, and therefore become more attractive as mates.) If you look at human cultures around the world, there are some things we have in common - music, language, stuff like that. But I think you could ask any anthropologist and find out that cultural norms are all over the place. For example, there are matriarchal societies, albeit less common than patriarchal (body size probably has an influence there - individuals are certainly limited in some ways by their biology). There are societies in which men dress up in fancy clothing, and women wear something dull. So it actually wouldn't make any sense for specific behavioral roles to be encoded in our genes.

What does make sense for social creatures such as ourselves is to absorb the rules for behavior in our culture early on in our development. I am forever astounded by the studies (or interpretations of studies) that claim that human male and female behavior is different genetically because they tested 2-year-olds. I have a 17-month-old who learns several new words a day. Every day of her life, she has heard the use of the pronouns "he" and "she" to refer to the different genders. Through the interactions of not only parents but any other adults or kids with her, she is told that she is a "she." What is a "she"? That is an idea she adds data to every day. It has something to do with clothes, something to do with speech, something to do with hair, something to do with body shape, etc. This is part of how she develops an idea of how she is supposed to fit in to her culture. I don't care how many studies are done on toddlers, I am convinced that kids from day 1 are developing an image of how someone like them fits into society. This is image is changing all the time, of course, because there is always new data to fit into their constructed idea of role and behavior.

So that's why I will always roll my eyes when some parent tells me that of course it's all genetic because their daughter loves dolls and their son loves trucks, and they never tell them what to play with, the kids just choose...

Labels: ants, brain, gender, sociality