468 The Ohio Journal of Science [Vol. XIX, No. 8, 



inhabit it but which are unable to reach it because of intervening 

 obstacles. Further, once having reached it, adult insects can 

 be semi-independent of a pond as a source of food. They can 

 frequent it, even lay their eggs, and thus start an entirely 

 aquatic fauna, and yet go elsewhere for their food. The absence 

 of fishes, predaceous enemies of insects, is also an important 

 factor. In point of numbers the aquatic insects Notonecta, 

 Corisa and Gyrinus were by far the most abundant. Freedom 

 from predaceous enemies permitted them to live and increase 

 without hindrance. The influence of such enemies is clearly 

 shown in a comparison of the one year with the five and the 

 ten year pond. Both of the latter are well populated with 

 fishes and in both, the strictly aquatic adult insects are entirely 

 absent from the area which the fish can reach. The ten year 

 pond is within a hundred yards of the one a year old and the 

 five year pond is over six miles away. It is thus not a matter of 

 location. In the fifteen year pond, on the other hand, the 

 fishes are bottom feeders and here surface insects again appear. 



The insect situation existing in these ponds does not agree 

 with results found by Shelford* in a series with sandy bottoms. 

 He states that aquatic insects are not numerous in the 

 younger ponds but that they increase in the older with an 

 increase in the vegetation. It should be noted, however, that 

 in the youngest pond of his series there were ten species of fishes 

 whereas in the oldest pond there were only four and these were 

 not especially insectivorous. 



The five year pond is primarily notable for the fact that 

 fishes were firmly established. They were the dominating 

 members of the fauna. Odonata nymphs had also become 

 established. Hydra was observed here first and so, too, were 

 nematoda and chaetopod annelids. Over most of the pond there 

 was no suitable environment for littoral animals. That the 

 absence of such forms was not a matter of distribution is to be 

 seen from the fact that at least some of these were present in 

 pools at one side of the pond. 



In the ten year pond emergent vegetation, lilies and reeds, 

 had gained a footing. Along with this appeared a new type of 

 mollusc, namely Ancyliis. So far as my observations went the 

 vegetation could not be correlated with the presence of any 

 other species. The most abundant members of the fauna were 

 chironomid larva and ephemerid nymphs. 



* Animal Communities of Temperate North America. 



