Richard See, age 14, of Lemon Grove, Calif., for his question:
What is inside an oak gall?
The plant world is at the mercy of many different galls. Some of these galls are nodules on underground roots; others are hard or soft bumps growing on leaves and twigs, stems and even blossoms. Galls may be the work of insects, molds or bacteria, and, because they feed upon the host plants, all these gall makers are parasites.
The oak apple is a round, woody globe attached to a twig or a leaf of a sturdy oah tree. It is not, of course, an apple at all. It is a gall, and the oak gall is the mysterious work of an insect. There are a number of different oak galls, each caused by a different insect. But the most common oak gall is caused by a flitting midge called the cynipid fly.
The mother cynipid fly Seeks out an oak tree when she is ready to lay her eggs. She may decide to start her nursery on an oak leaf, though she is more likely to select a tender twig. Trouble for the oak tree begins when the insect drills a hole and in it deposits an egg. Her work is done and she flies away.
The egg in its tunnel of woody tissue soon hatches into a tiny grub. Now the mystery begins. By some process unknown to science, the hungry grub forces the oak tree to produce a wad of woody cells. Soon the little grub is surrounded by a woody home which protects him from the outside world and also provides a pantryful of plant sap to satisfy his enormous appetite.
The larva of the gall insegt is sealed completely inside his round oak apple. He eats and eats until he reaches his full size. Then he begomes a pupa while he changes into a winged, adult insect. The inside of a woody gall is no place for a creature that can fly, so the small insect eats a tunnel and climbs outdoors where he spreads his wings and takes to the air.
Gallvaking insects., molds and bacteria are pests of the plant world, but some Of them are useful to us. Some gall makers attack and destroy goldenrod and other plants we rate as weeds. Oak galls are rich in tannic acid, and before the age of Chemistry they were used to tan leather and make certain dyes. The chemicals soaked frill oak apples are still used to make some of our best inks.