Abstract

Full, R.J. and Koehl, M.A.R. 1993. Drag and lift in running insects. J. exp Bio. 176, 89-103.

Drag and lift forces are always considered to have negligible effects on the power generated for terrestrial locomotion. We tested this assumption for two cockroaches, a fast and slow species. During escape running, the fast cockroaches' mechanical power output increases curvilinearly with speed and is greater than predicted from scaling relationships. We measured drag and lift forces on cockroaches in a wind tunnel at a variety of relative air speeds, angles of attack, and distances from the substratum that mimicked those of locomoting cockroaches. Both lift and drag increased with relative air speed and angle of attack. Although lift decreases the power required to run by reducing functional body weight, maximum lift was only 2% of body weight. Maximum drag, however, was 10% of the peak horizontal accelerating force measured for living animals. The additional power output to overcome drag can explain the elevated power output of rapid running cockroaches. Drag cannot be considerable negligible during terrestrial locomotion of small, rapid running insects.