08/23/2006
Praying, Preying and Popping
Two weeks ago, I mentioned encountering a praying mantis at our local mall. I wondered whether, if the mantis made its way into the mall, a sparrow that seems to have made a home inside the mall might eat it. I should have wondered if the praying mantis would become a preying mantis and turn the tables on the bird! In the September National Geographic there’s a picture titled “Bug Eats Bird” taken by Richard Walkup in a yard in West Chester, Pennsylvania. Sure enough, there’s a praying mantis (more precisely, a Chinese mantid) hanging down from a flower. The mantid’s forelegs are grasping a ruby-throated hummingbird. The preying mantis feasted on the bird until it was full, then dropped the lifeless bird to the ground. Mantids can grow to be as long as 5 inches, quite a sizeable insect but, with its green coloration, it blends in with the vegetation.
Praying mantises may look as though they’re praying with their forelimbs held out in front of them, but they are described in my 1962 World Book Encyclopedia as “cruel and greedy”. They eat all kinds of other insects, including garden pests, which make the mantid a welcome presence for gardeners. However, the female is indeed cruel and will gobble up her mate if she’s hungry, not what you expect of what looks like such a pious creature.
I pity that poor surprised hummingbird, hovering while sipping nectar from the flower, only to be grabbed by the superbly camouflaged mantid. Apparently, there’s another mantis-related predator only this is a shrimp – the mantis shrimp. I’m not familiar with this animal but it had the record for the “swiftest strike in the animal world”, according to an article by Sarah Yang on the UC Berkeley Web site. I was led to this site by an article in the August 22 Star-Ledger. The AP article was by Randolph Schmid and had the catchy headline “Before you can say ‘Chomp’ it’s all over”! It seems that an unusual ant, a trap- door ant known as Odontomachus bauri, has eclipsed the mantis shrimp’s record.
Regular readers will realize that I’ve been on an ant kick this summer, partly spurred by my friend Dan in Hawaii, who has a special interest in ants for some reason. I had decided enough about ants but this trap-door ant is a fascinating little critter, only about a third of an inch long and weighing around 12 to 15 milligrams. However, it can close its mandibles at an impressive 78 to 145 miles per hour. The researchers, led by Sheila Patek of UC Berkeley, claim this is the fastest self-powered predatory strike in the animal kingdom. Their work was published in the August 21 electronic issue of the Proceedings of the National Academy of Sciences. Purists might point out that falcons strike at speeds of up to 300 miles an hour but to attain that speed they have to start at high altitudes and gravity provides a big assist.
This trap-door ant utilizes only the energy stored in its body to get those mandibles moving and woe unto any insect in their range. While the speed of closing its mandibles is impressive, Patek points out that the truly impressive feat is the acceleration. We hear about cars accelerating to 60 mph in seconds. This trap- door ant gets its mandibles moving to over a hundred miles an hour in just 0.23 milliseconds (23 hundred thousandths of a second)! This corresponds to about a hundred thousand times the force of gravity. To achieve this impressive performance, the mandibles are cocked by relatively large muscles in the ant’s head and are released to spring shut when unlatched.
The trap-door ants in the study are from Costa Rica. Costa Rica was one stop on our cruise last year and my wife and I chose to go on an aerial tram through the upper reaches of the rain forest. It was very interesting but now I’m sorry I didn’t look down at the ground. Perhaps I would have seen some trap-door ants engaging in an activity that caused some hilarity in Patek’s lab. The ants not only use their fast-closing mandibles to nab prey. They can snap their jaws shut, propelling themselves spinning into the air as high as 8.3 millimeters and horizontally up to nearly 40 millimeters. The researchers liken this to a 5-foot-6- inch tall human jumping 44 feet into the air and traveling horizontally 132 feet! Get a bunch of the trap-doors together and they look like popcorn popping.
Two of the researchers, Andrew Suarez of the University of Illinois at Urbana-Champaign and Brian Fisher of the California Academy of Sciences observed the popcorn-like jumping of a group of the ants while they were collecting ants for the study in Costa Rica. They speculate that the group- jumping may be a defense mechanism to confuse predators. The ants don’t have any control over their flight pattern and can land on their back or their head – it doesn’t make any difference. They right themselves and go on their way.
The ants have evolved this type of escape maneuver in which they close their mandibles against the ground to send themselves flying away from an intruder. If the intruder is less intimidating, the ants may use a “bouncer defense”. In the bouncer mode, the ant, perhaps with a bunch of its colleagues, goes up to an intruder and strikes it, closing its jaws. The result is that the ant may get in a bit of a nip on the intruder but the ant still gets thrown off (bounces) into the air, though not as far or as high as in the normal escape jump.
If you’re wondering how they measured all these facets of the ant’s behavior, the researchers used super high-speed video cameras filming at 50,000 frames per second. (We watch normal movies filmed at 24 frames per second.) I’m sure the researchers will be filming trap-door ants from other areas in Central and South America. They want to see if ants in other locations have also evolved the use of fast-closing mandibles for both predatory and escape purposes.
Enough about predators. Back to West Chester. Sixty years ago, I was in West Chester and had a much more pleasant visual experience than watching a hummingbird die in the clutches of a bug. A college buddy and I were returning to Pennsylvania from a trip to Atlantic City, where we had enjoyed the beach and Harry James and his band on the old Steel Pier – no casinos in those days. We stopped for dinner at a restaurant in West Chester and at the next table were a half-dozen of the most beautiful girls we had ever seen. They were contestants in some sort of beauty contest and would not have been out of place were they entered in the Miss America contest back in Atlantic City. It’s the only time I’ve been in West Chester but the memory lingers on. (When my wife questioned the “most beautiful” phrase, I pointed out the “had ever seen” phrase signifying most beautiful to that point in time!)
Allen F. Bortrum
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