CHAPTER XIV 
PRAIRIE ANIMAL COMMUNITIES 
I. INTRODUCTION 
We have noted that a part of the region about Chicago is to be 
classed as savanna and that the savanna is made up of trees in groves 
and along the streams, and of forest margin and prairie. Prairie may 
roughly be separated into high and low. The low prairie commonly 
exists in depressions in the moraine, lower places in the plain of old 
Lake Chicago. They are usually covered with water in the spring. 
The high prairie is above water and is dominated by different plants. 
As the depressions are filled or become better drained, high prairie 
plants capture the habitat. 
II. PRArRIE FORMATIONS 
We have noted that the low prairie is covered by water in spring 
(Figs. 280, 281). As the water dries up, which usually occurs by the 
middle of May, the prairie plants begin to grow and the prairie animals 
make their appearance. This change does not take place abruptly, 
but gradually. There is a succession of adult-stage animals through 
the summer. This is what is known as seasonal succession. 
I. SEASONAL SUCCESSION 
When the snow melts in March and the frost goes out of the ground, 
the salamander (Amblystoma tigrinum) comes out of the ground and 
soon deposits masses of eggs in the water. The young of Eubranchipus, 
Cyclops, and rotifers appear after a few days and often reach adult size 
by April 1. On April 6, 1908, Mr. Dimmit found adult Eubranchipus, 
Cyclops, and rotifers in the pond south of Jackson Park. The sala- 
manders had disappeared. On April 12 three species of flatworms 
(Vortex viridis, Planaria velata Stringer, and Dendrocoelum) had appeared, 
and the first frogs were noted. On April 14 he found frogs’ eggs and 
the red crustacean (Diaptomus). Eubranchipus was at its maximum 
abundance. On April 19 he found Daphnidae, rhabdocoel worms, and 
tadpoles. On May 3 but few Eubranchipus were found. Diapiomus was 
plentiful, perhaps at its maximum abundance. Daphnidae was more 
abundant than before. Planaria were near their maximum. On May 10 
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