144 POND COMMUNITIES 
crustaceans constitute an important element in this association. The 
smaller amphipod (Hyalella knickerbockert) is abundant among the 
chara. The crayfish (Cambarus tmmunis) occurs here sparingly. In 
ponds there is an important element of small crustaceans that belong 
to the vegetation and the bottom; this element is composed chiefly of 
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REPRESENTATIVES OF THE SUBMERGED VEGETATION ASSOCIATION 
Fics. 89, 90, 91.—Larva of a midge (89), pupa of the same (90), the adult. 
Midges are inhabitants of the chara-covered bottom; enlarged about 4 times (after 
Johannsen, Bull. N.Y. State Museum). 
Fic. 92.—The eggs of the common large black horsefly on the tip of the bulrush 
stalk. 
Fic. 93.—The chara-inhabiting caddis-worm (Leptocerinae); enlarged as indi- 
cated. 
Fic. 94.—Ostracod (Notodromas monacha Miill.); 30 times natural size (after 
Sharp). 
Ostracoda (Fig. 94), which are small bivalved forms resembling the 
bivalved Mollusca. They form food for fishes to a small degree. 
Especially abundant just under the chara are the red water-mites 
(Limnochares aquaticus) (Fig. 80, p. 130). One sees numbers of these 
