3? 2 
IOWA ACADEMY OP SCIENCE 
wards to bring the breathing spiracle on the extremity of the 
body to the surface, or they swim about, coming to the surface 
at intervals where the water is deeper. They feed by sweeping 
microscopic organisms into the mouth. As a large portion of 
their time is spent on the bottom, and most of their feeding is 
done there, it seems best to include them in the bottom associa- 
tion. 
5. Simulidae — Black flies. Adults swarmed about in such 
great numbers on April 17 as to make it uncomfortable near the 
stream. They resembled Prosimulmm pecuarum Biley, but did 
not bite. 
Vertehrata. — The vertebrates were represented by two species 
of common frogs, the Leopard frog, Rama pipiens Sch., and the 
common tree frog, Hyla versicolor LeConte. The Leopard frog 
makes the marshes and brooks its normal habitat while the little 
tree frog takes to the water only during the breeding season. 
The eggs of Hyla were taken from one of the pools on April 17. 
These hatched in three days when taken into the laboratory. 
The stomach contents of two specimens of Rana pipiens Sch., 
taken April 24, tell the story of their food habits. 
Specimen No. 1. One May fly adult 
remains of six sowbugs 
one small terrestrial beetle 
one dipterous larva, probably Tipulid 
other unrecognizable material. 
Specimen No. 2. Larvse of Carabid beetle 
one spider and remains of two others 
two sowbugs 
one snail, Limnaea? 
remains of one Myriopod 
three small beetles, remains of one other 
The variety of these contents shows that the supply has come 
from both terrestrial and aquatic forms. The frog is therefore 
a most important member of the transition zone association. 
