Proc. Natl. Acad. Sci. USA 103, 12787-12792 (2006).
doi: 10.1073/pnas.0604290103 | PNAS :: Abs . PDF . Supp.Info. | CrossRef
PNAS online 20060821; Printed 20060822

Win with just one strike, a flash superstrike

It's completely inconceivable for a person to strike with a force 500 times the body weight, that is, for a 70 kg weight man, this nominal force should be as high as 3.5x10^5 N (35 ton). However, the trap-jaw ants (Odontomachus bauri) can produce a force 371 – 504 times their body weight with rapidly striking by a single jaw (average 47 mN; maxima ranged from 51 to 69 mN). This mechanical potential seems to be only but enough skill for trap-jaw ants to fight for their living.

Recently, S. N. Patek, A. V. Suarez and their colleagues used high-speed videography to view the behavioral details of the trap-jaw ants living in Central and South America. The data, reported in the 22 August 2006 issue of Proc. Natl. Acad. Sci. USA [ 1 ], is so impressive and has shown that the ants can use their hard jaws to strike ground or other substrate's surface, or the intruder with remarkable jaw-closing speeds ranging from 35.3 to 64.3 m/s and accelerations on the order of 10^5 g (g = 9.8 m/s^2). 

In the world of small animals like trap-jaw ants, this superstrike is powerful enough to knock away, stun or/and kill their enemy (insects etc.), or in a life crisis of meeting with terrible tongue of a lizard, result in strong ballistic propulsion to rapidly bounce themselves far away along with a high body-spinning rates, which the instantaneous angular velocities are from 2.85 x 10^4 to 4.73 x 10^4 rad/s. The average duration of a strike was 0.13 ± 0.05 ms with a minimum observed duration of 0.06 ms.

Concerning their body masses and lengths (on the order of 1cm), this response along with the following strike force and accelerations, jump speed and height, or the projectile distance are on the high end by comparison with other biosystems' movements by mantis shrimp (10^4 g, 23 m/s) (2), nematocyst stylet speeds (10^6 g, 18.6 m/s) [ 3 ] and fungal ballistospore launch accelerations (10^4 g, 1.5 m/s)  [ 4 ]. However, the flea may be a movement competitor with trap-jaw ant. It's difficult to give an accurate jumping data because there are so many species [ 5 ], but in a general evaluation from daily experiences, the flea can jump as much as the order of 20 cm vertically and 50 cm horizontally [ 6 ]. I remember a flea that I had seen more than twenty-six years ago. That flea deeply surprised me because I could not catch it at all. It urgently escaped by continually bouncing with decreased heights from about 70 cm at the first jump to 30 cm at last and about 50 cm horizontal step (also decreased gradually in the following steps); every step took less than 1 second along with a short rest after each jump.

For the present study, it should be noted the biological implications of two jaw-striking jumps. These two jumps, named as defense and escape jumps by the researchers, have evidently jumping parameters. The defense jumps with take-off angles of 27° yield low heights (1–6 cm) and substantial horizontal trajectories ranging from 5 – 40 cm, whereas escape jumps (take-off angles of 76°) covered shorter ranges (<1– 5 cm) and reached greater heights (6–8 cm). The researchers deduced that these versatile but exceptional jumps should imply a degree of specialization for speed that is correlated with specific predatory strategies, and more importantly, a strong preference and correlations due to evolutionary tradeoffs, evolutionary origins, and higher rates of lineage diversification all have been attributed to multifunctional morphology.

However, as a phenomenological study on trap-jaw ants, there are plenty of open questions to be addressed beyond this interesting progress. Just how subtle is the mechanical and biological system of the super jaws? And how effective is the energy-releasing for firing flash jaw-striking and why? ♦

* Lin Pu is in the Physics Department of Nanjing University, Nanjing 210093, CHINA.

References  

Citation

L. PU

Lin PU. Win with just one strike, a flash superstrike. Scidea Sketch 1 (1), ss20060822a1 (2007). 

♦ doi: 10.3128/ss20060822a1 | Scidea ::  Abs . Full | CrossRef
♦ ISSN: 1992 - 8548