Insects Do 'The Wave'
A popular activity that has arisen in recent years at athletic events is the so-called “wave.” Members of the audience participate by extending their arms above their heads in sequence such that a wave is created. It gives the audience something to do when the action on the court or field is a bit on the dull side.
Insect caterpillars use their version of the wave to accomplish biological activities such as crawling and beating of the heart. Caterpillars are made up of a series of segments, and most have legs or leg-like protrusions on many segments. When a caterpillar wants to move forward, the action begins at the rear. The last segment moves forward, creating a domino-like chain reaction as each segment appears to be pushed forward. Once the head moves forward, the process begins again, creating a sequence of waves through the body of the caterpillar.
The same process is used by the caterpillar to force hemolymph through it's heart. The caterpillar heart is a tube-like affair that is open at both ends. The heart picks up the fluid at the back, and a series of muscles contract in sequence to force the 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 of 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 using 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 difficult to tell if a slow-moving millipede is really in a hurry, it will have several waves moving through its legs at once.
In insects, millipedes, human digestive tracts, and athletic contests it appears a wave is a good way to get things going.