MATURE COMMUNITIES 



147 



Char a. 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 trmicatum, 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 



Fig. ioi. — Showing Pond 14 at moderate low water. In contrast with Pond 1 

 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. 101), 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 



