George Kantor, age 10, of Grand Forks, N.D., for his question:
DO INSECTS HAVE BLOOD?
Inside an insect's body is a circulatory system through which blood is carried. An insect's blood doesn't flow through veins and arteries as our does. Blood fills the whole cavity of the insect's body and bathes all the organs and muscles.
The blood is circulated by a long tube that lies just under the exoskeleton of the back. This tube extends almost the entire length of the body. The pumping part of the tube lies in the abdomen and is called the heart. The front part of the tube extends into the head and is called the aorta.
Blood enters the tube through little openings, called ostia, along the sides. The openings have valves that allow blood to enter the tube, but not to flow out. As the heart contracts, the blood is forced along the tube and out through the aorta.
The blood first bathes the brain and then flows to other parts of the body. It then re enters the tube through the ostia.
An insect's blood, like ours, carries food and waste products to and from the cells of the body. But unlike our blood, it has little to do with bringing oxygen to the cells. Insects' blood is greenish, yellowish or colorless. Few insects have red blood. Our blood contains a red pigment called hemoglobin, which carries oxygen to the cells.
Insects are cold blooded animals. That means the internal temperatures of their bodies varies according to the temperature of the surrounding air.
An insect's body temperature rises in hot weather and falls in cold weather. An insect will become more active when the temperature rises and it will slow down as the temperature drops.
An insect breathes by means of tiny holes, called spiracles, along the sides of its body. Each hole leads into a large tube called a trachea.
As part of the respiratory system, the large tubes divide into small tubes, which in turn divide into still smaller tubes that branch out to all of the cells of the body. This system of tubes carries oxygen to the cells and takes away carbon dioxide.
The nervous system of an insect consists of a brain, located in the head, and two nerve cords that lie side by side along the floor of the thorax and abdomen. The brain receives information from the eyes and antennae, and controls the insect's body activities as a whole.
Another nerve center in the head is connected to the brain and controls the insect's mouth parts. Each of the two nerve cords contain a cluster of nerve cells, called a ganglion, in each segment of the thorax and abdomen.
An insect's muscular system is made up of several hundred to a few thousand small but strong muscles. Grasshoppers have about 900 muscles and caterpillars have from 2,000 to 4,000. Man has fewer than 700 muscles.
Many insects can lift or pull an object 20 or more times heavier than the weight of their bodies. Few men can lift a weight heavier than the weight of their bodies.