248 THE UNIVERSITY SCIENCE BULLETIN. 



Culture 17165. (Chironomus.) 

 History aiid Diagnosis. Early in the studies on the boatmen, it was 

 found that hungry bugs would eat Chironomus larvas. In this experiment 

 some sand grains were placed in the bottom of a stender dish, and six 

 Chironomus larvse added. 



Corixids Added. Placed six P. buenoi here that had been in clear 

 water two days. In two hours only three Chironomus larvae remained. 

 These were fortified beneath sand grains. These midge larvae live in the 

 sludge where Corixids forage. They live in tubes of their own spinning, 

 and occasionally are eaten by the boatmen when the bug comes upon them 

 in the course of its feeding. 



Culture 1650. (Balanced Aquarium.) 

 History and Diagnosis. Into a circular glass aquarium jar, 9%x8 

 inches, there had been placed about May 1 one of the Characeae (Nitella) 

 and some clear pond water. The cultux-e came under observation the 

 latter part of May, at which time the Nitella was still a thriving plant, 

 and a small quantity of brownish sediment was upon the bottom of the 

 jar (arranged in a ring perhaps two inches broad around it). The con- 

 tainer was kept nearly full of water by additions from the top. Corixid 

 nymphs in their first instar had hatched from eggs brought in on the 

 Nitella, and continued their development till they became adults. Bits 

 of the carapace of a crayfish bearing eggs of Ramphocorixa acwminata 

 were then added, and this species brought to adult stage. This culture 

 then has considerable interest from the fact that two generations of 

 Corixids were reared in it, one of A. alternata, a clear-pool type, and one 

 of R. acuminata, a stagnant-pool type. 



The Nitella gradually disintegrated, adding its parts to the deposits 

 in the bottom of the jar, until by July 23 little was left of it. Surveys 

 from time to time disclosed the following in the deposits: Much dis- 

 organized plant matter, a few green spores of Algas, slender empty fila- 

 ments of Algje, some Pediastrum, various diatoms (abundant), and now 

 and then the shell of an Ostracod. Ostracods and snails the only forms 

 of animal life noted. The sediment, notably clear of animal life, adds 

 another feature to the interest of this study. Corixids were observed 

 repeatedly to feed upon the brownish deposit. Corixids were maintained 

 in this jar continuously for nearly four months. 



Corixids Added. Corixids of two species, A. alternata and R. acum- 

 inata, were reared here. Some of the bugs were maintained here for 

 four months. These bugs obtained their food from the deposits at the 

 bottom. They did not prey upon the Ostracods feeding upon the sides 

 of the jar. 



CONCLUSION. 



After carefully checking the results of feeding experiments 

 it is safe to note the following : 



Corixids sweep in the organic ooze of the pool with its at- 

 tendant populations, both plant and animal, the bulk of the 



