Cockroache; Ecology, behavior & history - W.J. Bell

TWO
Locomotion:
Ground, Water, and Air
i can walk on six feet
or i can walk on four feet
maybe if i tried hard enough
i could walk on two feet
but i cannot walk on five feet
or on three feet
or any odd number of feet
it slews me around
so that i go catercornered
—archy, “a wail from little archy”
Cockroaches were once placed in the suborder Cursoria (Blatchley, 1920) (Lat., runner)
because the familiar ones, the domestic pests, are notorious for their ground speed on
both horizontal and vertical surfaces. Indeed, the rapid footwork of these species has
made cockroach racing a popular sport in a number of institutions of higher learning.
Like most animal taxa, however, cockroaches exhibit a range of locomotor abilities,
reflecting ease of movement in various habitats. On land, the limits of the range are mirrored
in body designs that maximize either speed or power: the lightly built, long-legged
runners, and the bulkier, more muscular burrowers. There is a large middle ground of
moderately fast, moderately powerful species; however, research has focused primarily
on the extremes, and it is on these that we center our discussion of ground locomotion.
We touch on cockroach aquatics, then address the extreme variation in flight capability
exhibited within the group. Finally, we discuss ecological and evolutionary factors associated
with wing retention or loss.
GROUND LOCOMOTION: SPEED
Periplaneta americana typifies a cockroach built to cover ground quickly and is, relative
to its mass, one of the fastest invertebrates studied. It has a lightly built, somewhat fragile
body and elongated, gracile legs capable of lengthy strides. The musculature is typical
of running insects, but the orientation of the appendages with respect to the body differs.
The middle and hind pairs point obliquely backward, and the leg articulations are
placed more ventrally than in most insects (Hughes, 1952; Full and Tu, 1991). Periplaneta
americana has a smooth, efficient stride, and at most speeds, utilizes an alternating
tripod gait, that is, three legs are always in contact with the ground. The insect can stop
at any point in the walking pattern because its center of gravity is always within the support
area provided by the legs. At a very slow walk the gait grades into a metachronal
wave, moving from back to front, that is, left 3-2-1, then right 3-2-1 (Hughes, 1952; Del-
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