Caterpillars do march on their stomachs

LIKE armies, caterpillars march on their stomachs - only they do so literally, scientists have learned.

From the outside, the grubs appear to crawl in back-to-front waves of motion that propel their bodies forward. But that is only half the story, research has shown.

Imaging studies show that a caterpillar's gut moves forward in advance of the surrounding tissues, shifting the creature's centre of gravity.

In effect, when the caterpillar walks, its stomach leads the way.

The "two body" system of locomotion has not previously been seen in any animal, say US scientists.

Although it is not yet clear how the mechanism provides an evolutionary advantage, they believe it could help the design of soft-bodied robots., the scientists wrote in the journal Current Biology.

They suspect that other kinds of caterpillar and possibly soft animals like leeches employ the same system.