150 American Fisheries Society 



and Chironomus, species nigricans. Their habitat was also in the 

 upper strata of the ponds among the algae, or scums. 



For the purpose of tabulating the data on the kind of food 

 taken by the chironomid larvae which at the time made up a large 

 percentage of the food of the young fish, a suitable number for 

 examination were selected both from their natural habitat in 

 the ponds and from the contents of the fish stomachs. They are 

 such voracious and continual feeders that in fresh specimens their 

 food content is easily ascertained. A larva is mounted in water 

 on a glass slide and covered with a cover slip. The'n, by exerting 

 gentle pressure on the cover in the region of the rear of the body 

 and pressing forward, the contents are forced out of the alimentary 

 canal. Thereafter the problem resolves itself into one of identifica- 

 tion of the algae present. 



By reference to the table it is seen that the algae Mougeotia 

 and Oedogonium are highly prized as food by the species of 

 chironomids indicated. Mougeotia is a very delicate alga and the 

 larvae prefer it to all others when it is present, as was observed 

 when rearing numerous larvae in the laboratory in aquaria, where 

 a mixed supply of algae was provided. The larvae reared in this 

 way always sought their forage among the filaments of Mougeotia 

 which they applied to their larval cases as a reserve. Oedogonium 

 is the other favorite alga with these chironomids. Spirogyra, 

 desmids and diatoms appear to be taken in lesser amounts by 

 the species of larvae under observation. Other species, doubtless, 

 make use of them in larger measure and at different seasons. 

 As our knowledge of the feeding habits of the chironomids becomes 

 known the variety of algae taken as food will be found without 

 doubt to be very great. This table indicates the forage ground 

 of but three species out of a probable host which subsist on the 

 common algal mats of our ponds, and signifies the value of these 

 plants in the ponds in terms of fish food. 



There are some species of algae which, so far as I am aware at 

 present, do not enter directly to any great extent into the forage 

 of the chironomid larvae. They are the coarser forms, the 

 Cladophoras, Pithophora, and the like, coarse in texture and difficult 

 to appropriate for food, but valuable in the economy of the pond 

 since they afford lodgment upon their filaments of the useful 

 diatoms. 



