The heart picks up fluid at the back, and a series of muscles contract in sequence to force fluid out the front end of the tube where the brain is located. Beating of the caterpillar heart is not unlike getting the last bit of toothpaste from the closed end of a nearly empty toothpaste tube. The process requires a wave action along the tube. We humans have a very similar process in our digestive tracts. The muscle contractions that keep the food moving through our systems occur in waves known as peristalsis.
Peristalsis is defined as a peculiar worm-like wave motion of the intestines.
Such action is not limited to insect caterpillars and human digestive tracts. Many- segmented organisms move sing peristaltic contractions. Earthworms are good examples. Millipedes also coordinate their many legs through peristaltic wave action. When a millipede is in a hurry, and it is sometimes hard to tell is a slow moving millipede is in a hurry, it will have several waves moving through its legs at once.