Karen Butler, age 10, of Tucson, Arizona, for her question:

Are insects warm or cold blooded?

A warm blooded animal has a built in biological thermostat that keeps his body at its proper temperature. In cold weather, his blood is made warmer than his surroundings. In hot weather, his body has automatic devices to lower his blood temperature. Nature's cold blooded creatures do not have these built in features. In cold weather their blood is as cold as the air and the ground. In hot weather their bodies get as hot as their surroundings. Only the birds and the highly advanced mammals have built in thermostats. The insects and all the less advanced creatures are cold blooded animals.

The insects outnumber all the other animals in the world. And all of them have learned to cope with their cold blooded problem. There are perhaps half a million insect species. Their watery blood may be tinged with yellow or green or some other color. But it circulates freely only when the surrounding weather is warm. In cold weather, the bugs and beetles, the flies and other insects become slow and sluggish. Many insects avoid the winter season as eggs, as silky cocoons or crusty crysallises. In mild climates, some species spend the winter as grubs or wingless nymphs in the ground.