EPHEMERID^E. 
137 
When we leave the surface, we find a number that live in the middle 
depths ; the peculiar mining larva of Dorycera, the red Chironomid 
larvae found in the soft stems of aquatic plants, the larvae of Ephemeri- 
dcv in the holes in the bank, the many larvae in masses of algae or weeds 
(Ceratopogon, Acentropus, Hydrocampa, Cataclysta, Paraponyx, Nym- 
phula and Simulium ), the few larvae that live actually free in the water 
in the middle depths (Corethra and Chironomid larvae), are examples of 
insect's neither dependent upon the surface for air nor finding food 
at the bottom, and which are commonly obtained with a net in the middle 
depths. 
There are also the insects in the depths or on the bottom ; the Per- 
lid larvae are under stones ; the mud-loving Sialidce , the larvae .of cad¬ 
dis-flies and dragon-flies are found on mud ; some are found only at the 
bottom of shallow running water, including caddis larvae, the nymphs 
of Odonata , Perlidce and Ephemeridce , as well as such aquatic Hemero- 
biides as are not found in sponges. 
Finally, there is the remainder, which are at all depths except near 
the surface, which range over the bottom and middle; these include the 
more active Odonata and Trichoptera, the larvae of Haliplidce, Gyrinidce 
and Parnidce, as well some of the Hydrophilidce (Berosus). A far larger 
part of the aquatic fauna would naturally come within this last division 
were one to go minutely into it, which is impossible in this place. 
Sufficient has been said to show that aquatic insects live in a world 
of their own, one as complex in its internal relations as that of the land ; 
we find herbivorous insects, preyed on by carnivorous ones, occasionally 
attacked by parasitic ones ; it is a teeming world of life of all kinds, of 
immense interest from every point of view and especially so from the as¬ 
pect of the immensely ingenious contrivances by which insects obtain 
their air supply. But it is a subject which has been scarcely touched 
in this country, though there are unrivalled opportunities at almost all 
times ; we anticipate that the investigation of how these insects pass 
through the time when tanks dry up will yield some extremely interest¬ 
ing results, and we may hope that, though there is no economic side to it, 
this fascinating branch of entomology will some day be attacked. 
Ephemerid^. —May-F lies. 
.Slender insects with large forewings and small hindwings. The antennae 
are short. There are two or three long processes on the abdomen. 
Tarsi four or five jointed. Larva aquatic. 
This is the last family in which the wings are formed in the active 
nymph outside the body as in Orthoptera. The wings are, in repose, held 
