Robert Hall, age 7, of Chateauguay, Quebec, Canada, for his question:

What causes blobs of spit on the leaves?

These frothy blobs are made by small insects that sip sap from the . leaves. Some people call them spittlebugs. Others call them froghpppers because they hop about like miniature frogs. A mother spittlebug lays her eggs on a green stem and uses the bubble blowing gadget in her tail to cover them with frothy foam. Some experts say she lashes her tail end from side to side to whip the moisture into a sudsy lather. Some experts say that the bubbles form as the liquid comes out of her tail.

In any case, the gob of froth hides the eggs and protects them from the weather. They hatch into tiny green babies called nymphs. And, chances are, a baby nymph will make a new blob of spit and hide himself inside his own foamy home. Now and then, he comes out and hops around to get some ex¬ercise. After he sheds his skin a few times, he becomes a dark brown, ob¬long shaped, grown up spittlebug.