Abstract

Full, R.J., Yamauchi. A. and Jindrich, D. J. (1995) Single leg force production: cockroaches righting and running on photoelastic gelatin. J. exp. Bio. 198, 2441-2452

Single leg force production by six-legged cockroaches, as well as by some other small insects, can be similar to the relative single leg forces produced by two- and four-legged vertebrates that are almost 1000 times more massive. Leg number and body mass alone, however, appear to be insufficient to explain the variation observed in relative leg force production at a given body mass, because enormous diversity in musculo-skeletal parameters exists. The maximal relative leg force of the cockroach B. discoidalis during righting was at the low end of a 100-fold variation observed for smaller insects wedging (pushing through a small crevice) and pulling loads. Thus, this cockroach can be characterized as a moderately strong insect with the capacity for relatively high speed. Results from the present study question the predictive strength of the simple geometric scaling arguments involving a strength:weight ratio as they are applied to small arthropods and encourage further consideration of the importance of leg number, muscle force production and mechanical advantage in the derivation of general principles of leg performance.