Eric Hodson, age 10, of Penticton, B.C., Canada, for his question:

Which snakes are called vipers?

Any snake may be called a serpent because all snakes are classified in the suborder Serpentes. But strictly speaking, the name viper belongs to the minority of poisonous snakes    and even some of these are not classified as vipers. According to scientists, the true vipers are a group of poisonous snakes native to the Old World. The pit vipers are a group of New World snakes.

The true vipers of the Family Viperidae strongly resemble our native rattlesnakes. However, they have no rattles, though some can shake their scaly tails to make a hissing sound. Our rattlers are classed as pit vipers because they have hollow dents in their heads, fitted with sensitive nerves to detect warm blooded victims. The true vipers do not have this special sensory organ. However, their fangs are longer and the largest true viper can inflict a deeper, more dangerous bite than even our deadly diamond back rattler.

Lost snakes keep to a fairly small range. But the common viper, alias the adder, ranges wide and high. He is found throughout Europe as far north as the Arctic Circle, two miles high in the Alps and eastward to the shores of Asia. Though only about two feet long, he is a very savage creature, always eager to strike. Like most vipers he is handsome. As a rule his back is marked with a long zigzag band bordered with rows of black buttons.

This adder viper likes dry heaths and moors and enjoys basking in the sunshine. He becomes alert after dark, when he goes hunting for rodents, snails and lizards, frogs and worms. Mrs. Adder gives birth to live babies, each wrapped in what looks like a ' clear plastic bag. The sturdy youngsters rip themselves free and start forth to hunt. Each has enough venom to slay four mice. Some observers claim that young adders wag their tail to lure victims within striking distance.

The asp adder prefers the warmer regions of southern Europe. This bad tempered snake is reddish brown and perhaps a yard long. In far away India, his cousin the Russell's viper is feared as greatly as the dreadful cobra. This handsome five foot snake is pale brown, with black bands bordered with gold or white. Most of the world's true vipers live in Africa    in secret burrows, half hidden in the sands or coiled up in piles of trash. One of these is the gaboon, the giant of the viper family. This dangerous character may be five or six feet long.

All the true vipers tend to have thick, wide bodies and tiny pointed tails. Most, but not all of them are savage creatures. But several small vipers and at least one large one tend to be rather timid and shy away from people. However, they strike when provoked    and the bite of any viper is deadly dangerous because these snakes have extra long fangs and extra strong venom. Many victims die without speedy medical help.

The puff adder of Africa has a thick body, adorned with a pattern that resembles rows of pale half moons in a mackerel sky. This venomous viper is in no way related to the harmless and helpful puff adders of America. Our so called puff adders are non poisonous and spend their time controlling the ratty rodent populations.