STONEFLY nymphs live in the running water of rivers and streams. You will not find them in quiet ponds, but you may find them in a wide pool in a brook or creek through which the water runs continuously.

You may find it difficult, at first, to tell a stonefly nymph from a mayfly nymph, be­cause you often find both clinging to rocks in running water.

Remember that the common mayfly has seven pairs of leaf-like gills on the sides of its abdomen and one claw on the tip of each foot.

The stonefly nymph has two claws on each foot, but some nymphs are so small that it is difficult to distinguish them by their two claws alone, so you must look for their gills. They do not have leaf-like gills. Their gills are thread-like and are usually found on the thorax, at the bases of the legs. If the nymph is very small, you may not be able to see the gills at all.

Large stonefly nymphs are sometimes as much as two inches long. Others measure less than one-half inch in length. Like may­fly nymphs, they have wing pads, and grad­ually develop into adults. A stonefly nymph usually lives in the water a year or more before it is fully developed. It does not molt a second time after emerging from the water, as a mayfly nymph does. Although it has biting mouthparts, it is doubtful wheth­er it eats much or lives very long.

Some stonefly nymphs are vegetarians; others are carnivorous. You cannot keep them alive very long in an aquarium unless you have running water. For this reason you may not be able to tell whether the stoneflies in a particular stream which you have been watching eat vegetable or animal matter.

If you are really curious about the habits of any animal you are studying, you can build a "cage" and keep him in it in his own home pond or stream. One scientist, Dr. James G. Needham, has used such cages to study the life histories of various fresh­water animals.