Rajat Mittal, a mechanical engineering professor at Johns Hopkins University, first became interested in spider crickets, sometimes called camel crickets, as a homeowner.
The crickets are a highly successful invasive species, and one of the places they invaded was Dr. Mittalâs basement.
He was trying to get rid of them, but, because he studies flight and swimming and other movements, he couldnât help but notice how well they jumped â up to about 60 body-lengths â compared with American crickets. âThe thing that really got my attention,â he said, âis that they seemed to mostly land on their feet.â
He brought them into his laboratory and not only figured out what they do, but produced some enchanting slow-motion video of their movements in the air.
Dr. Mittal is no stranger to the study of aerodynamics. He did work for the Army on the way parachutists maneuver in free fall, using their arms and legs. The crickets do too, although with six legs and two antennas, he pointed out, they have more appendages at their disposal.
Dr. Mittal has three high-speed cameras in his lab and Emily Palmer, an undergraduate at Johns Hopkins, and Nicolas Deshler, a high school student at Washington International School, spent several months getting the crickets to jump. In all, they shot about two dozen good videos.
Dr. Mittal and his colleagues are still doing the mathematical analysis, to be presented at a poster session at a Nov. 22-24 meeting in Boston of the American Physical Societyâs Division of Fluid Dynamics. But, he said, a few things are fairly obvious.
First, the crickets try to become as streamlined as possible when they take off. But before they hit the peak of their jump, they move their limbs out from their body to stabilize themselves at an angle of about 55 to 60 degrees.
And they keep that angle until their hind feet touch the ground. âItâs like an aircraft landing,â Dr. Mittal said. Touching down nose first would be disastrous.
The result is that as soon as they land on their very strong hind legs, theyâre ready to jump again. This pattern holds true when they can jump straight forward, he said.
If they are disturbed from the side or from the front, âthey just take off and they donât really care.â Then, landing can be a problem. Dr. Mittal hasnât seen really bad crashes, but in collecting the crickets, he said it is common to find animals with damaged limbs, and bad landings could be a cause.
Any new understanding of movement and aerodynamics in insects can be potentially useful in designing small robots. But, Dr. Mittal said, there is something else to be gained from the study of natural movements in animals you thought were pests: unexpected beauty.