MATURE COMMUNITIES 147 
Chara. Their place is taken by other bivalves, viz., the Sphaeridae, such 
as Musculium partumeium, which lives in the humus of the bottom, and 
Musculium secure and truncatum, which live in the vegetation and are 
able to climb on the vegetation and on the side of aquarium jars. 
In the early phases, shrubs and young trees have begun to grow by the 
sides of the ponds and these from time to time fall into the water, thus 
forming a resting-place for many forms that are not found in the other 
situations. Diving spiders (Fig. 95) are common on the bulrushes which 
Fic. tor.—Showing Pond 14 at moderate low water. In contrast with Pond tr 
we see that it is choked with emerging vegetation and the margin occupied by shrubs 
and bulrushes, etc. 
are here growing on a bottom of humus outside leaf-bearing plants 
(Fig. tor), inside the shrubs. These spiders dive for the immature 
aquatic insects which are here at their maximum. We find numerous 
damsel-fly nymphs and dragon-fly nymphs, both the creeping form (Leu- 
corhinia intacta) (Figs. 96, 97,98) and the climbing form. The burrow- 
ing dragon-fly nymph has gone, or is present in small numbers only, and 
there are but few May-fly nymphs. Those that persist creep about on 
submerged sticks in company with Amnicola and are especially likely to 
occur in the earlier phases of this community. With these occur the 
