June, 1919] Fauna of Rock Bottom Ponds 469 



The ten year and the one year ponds make an interesting 

 comparison because of the fact that they he side by side and 

 both offer a bleak habitat. Their chief physical difference was 

 in size. Faunally they differed most markedly in respect of 

 their hemiptera, larval beetles, diptera and ephemeridae. The 

 two species of hemiptera so abundant in the one year pond 

 were not in the ten year pond. The species of diptera and 

 ephem-erid£e were not the same in the two ponds. There were 

 no larval beetles in the ten year pond. The absence of these is to 

 be correlated with the greatly reduced number of adult species 

 represented, as compared with the one year pond. In point of 

 numbers the gyrinid and the dytiscid larvae composed the larger 

 part of all coleopterous larvae in the one year pond. Adults of 

 neither of these groups were in the ten year pond. 



Several factors are probably responsible for the absence of 

 the beetles from the ten year pond. The presence of fishes 

 undoubtedly plays a large part. It is also to be noted that some 

 of the species in the one year pond apparently prefer clear water. 

 For example, Blatchley* states that Philhydrus rises to the sur- 

 face when the water becomes turbid. The water in the ten year 

 pond was decidedly turbid and this may therefore be a factor. 

 Furthermore, there was little in the way of debris about the 

 edges of this pond to attract 'the shore inhabiting species. 



Two of the three species of ephemerid nymphs in the one 

 year pond were not in any of the others. Their adults also were 

 not numerous in the region. Heptagenia, the form in the ten year 

 pond, was the most abundant member of this group in the 

 region. Its chances for general distribution as a nymph were 

 therefore greater and, as matter of fact, it was one of the types 

 found in all of the ponds. Possibly the regional scarcity of the 

 two species in the one year pond was a factor responsible for 

 their absence from most members of the series. 



In the fifteen year pond there were certain abnormal con- 

 ditions which perhaps made it hardly a fair test of pond develop- 

 ment at this age. It was the first pond offering conditions 

 suitable for microdrilus oligocheta. This is said not merely 

 because Lumbriculus was present but also because under the 

 conditions it would have been surprising to have found them 

 in the younger ponds. Turtles were seen for the first time and 

 catfish also found a suitable environment. 



"Coleoptera of Indiana. 



