[Illustration: _Fig. 51. The dobson makes no pretensions to beauty. (Natural size)._] Let us leave the quiet, restful pools and the sluggish bays, and follow the hurrying water to the rapids. Every stone changes the course of the current and the babble makes glad the heart of the wayfarer. Let us "leave no stone unturned," until we have routed from his favorite haunt that genius of the rapids, the dobson. (Fig. 51.) These creatures bear other common names. They are prized by fishermen in the black bass season. Dirty brown in color and frankly ugly in appearance and disposition, these larvæ, for such they are, have little to fear from the casual visitor at the water's edge. When a stone is lifted, the dobsons beneath it allow themselves to be hurried along for some distance by the current. The danger over, they "catch hold" and await their prey farther down stream. In spite of their vicious looking jaws these insects are not venomous. At the very worst they could do no more than pinch the finger of the unwary explorer. [Illustration: _Fig. 52. May-fly nymph._ (_Three times natural size_).] When the dobson is full grown, it is called a hellgrammite fly or horned corydalis. It has lost none of its ugliness, though it has gained two pairs of thin, brownish-gray wings, and flies about in the evening. It has been known to create some consternation by flying in at an open window. It is harmless and short-lived in the adult stage. Upturned stones are likely to bring to view other strangers. Lying close against these wet stony surfaces one usually finds young May-flies. (Fig. 52.[15]) These, like the young dragon-flies, are called _nymphs_. [15] Figures 52, 53 and 54 are adapted from Dr. R. Leuckart's Zoological Charts. When they are ready to leave the water they make their way to the shore, and, clinging to some convenient tree trunk or building, they shed their nymph skins. I have seen trees and buildings on the banks of the St. Lawrence river literally covered with these cast skins. In the early morning in June and July one may watch the molting process, the unfolding of the gauzy wings, and the unsheathing of the long filaments. (Fig. 53.) Do not believe that May-flies are harmful. They are sometimes too numerous for comfort at summer resorts where myriads of them swarm about the lights; but stories of their stinging and biting are entirely without foundation. They are short-lived in the adult stage. The name of the family to which they belong, _Ephemeridæ_, suggests their ephemeral existence. It is of these that poets have sung. Stone-fly nymphs, also, cling closely to the flat stones. The cast skins of these are frequently found on the banks of streams. They resemble the May-fly nymphs but can be identified by a comparison with these illustrations. (Fig. 54.)