84 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
The larvae, or naiads, have chewing mouth parts, whereas those of 
the adult are vestigial. AIl the larvae are aquatic, often extremely 
abundant, especially in cool streams. They are provided with gills 
and live under stones or among the debris on the stream bottom where 
they eat decaying vegetable matter. 
The peculiar dipping flight of the adults of some species, as they 
hover over the water surface e, 1s quite distinctive. Another pecuharity 
is that many of the adults molt after attaming full development. 
During the mass emergence or flights of the adults, the naiads can 
be seen emerging on the surface of ‘the water in great numbers, where 
they cast off ‘their skins and rise into the air. Any experienced trout 
fisherman has learned to watch for the so-called flights of Mayflies 
on a warm, calm evening, and to take advantage of the coincident 
voracious feeding of the fish. These insects form a very substantial 
food item for many fish. 
THE STONE FLIES 
OrpdER PLECOPTERA 
The stone flies have four wings with numerous cross veins: the rear 
wings are folded in pleats (as the technical name of the order implies) 
when at rest, and are 
usually the larger (fig. 
10). They have chew- 
ing mouth parts, and 
many-jointed cerci. The 
metamorphosis is in- 
complete. 
The flat-bodied, 1m- 
mature stages (nailads) 
of stone flies are all 
FicureE 10.—A stone fly, Taeniopterya2 pacifica, aquatic and can be 
x 3. found abundant under 
stones in the swift water 
of streams. They are an important source of fish food, and can al- 
ways be depended on by the angler when other forms of bait fail, or 
when the trout are reluctant to take a fly. A few luscious naiads of 
these insects will often fill the creel. 
Some species, like the Mayflies of the preceding order, appear in 
flights of enormous numbers. Many are rather cool-weather insects, 
and on the first warm, sunny day of spring, even though ice is still 
floating in the water, the smaller species of stone flies may be observed 
crawling out of the water’s edge to shed their skins and listlessly take 
to flight, and may annoy the ‘angler by crawling up his trouser leg. 
THE DRAGONFLIES AND DAMSEL FLIES 
ORDER ODONATA 
The dragonflies and damsel flies are characterized by two pairs of 
membranous wings of about equal size and abundantly net-veined. 
They have chewing mouth parts and go through an incomplete met- 
amorphosis. The larvae, or naiads, are aquatic. 
Dragonflies and damsel flies are abundant and characteristic insects 
around slow streams and ponds. The former are active, strong fliers 
