22 BULLETIN OF THE BUREAU OF FISHERIES. 



Then siik is spun by the obvious use of the prolegs, as in the case of Chironomus lobiferus. 

 Each addition of debris is fastened in place by silk which is attached to the older parts 

 of the burrow and spun out and part way around this material. In this way the larva? 

 construct long tubes that give them protection from enemies and at the same time 

 help support them on the surface of the soft debris where they are usually found. The 

 tubes are often U-shaped, and thus serve to bring in fresh water from which the larvae 

 are able to carry on their respiration while living among decaying organisms at the 

 bottom. 



FEEDING HABITS. 



The author has found it exceedingly difficult to satisfy himself that the members 

 of this group are not really similar in habit to those included in Group I, but repeated 

 experiment has convinced him that their habits are distinct. When a large number 

 of these larvae are scraped up together with a mass of the surrounding debris and then 

 spread out in a shallow dish, they literally spin every bit of the debris into loose inter- 

 woven U-shaped burrows. When one tests the current in these burrows, the water is 

 found to be flowing through them in a definite direction. 



Methods have been repeatedly tried to get these larvae to adapt themselves to glass 

 tubes of the sort used so successfully with Chironomus lobiferus, but in no case have 

 these experiments succeeded except when sufficient debris was present to make it possible 

 for the larva to completely conceal itself. 



Several larvae were put upon pure sand with the hope that it would furnish pro- 

 tection, if that was what was desired, and at the same time fail to serve as food. The 

 larvae were obviously not well satisfied with their surroundings and moved about over 

 the surface apparently in search of more suitable conditions. In removing the larvae 

 from their burrows a small piece of the organic debris of which their tubes are character- 

 istically composed was left adhering to one of them. This the larva kept clinging to 

 and trying to roll up into a burrow. The other larvae as soon as they encountered this 

 debris attempted to get possession of it; after a few hours they all made burrows out 

 of sand. The current was tried by means of powdered carmine but without satisfactory 

 results. 



In another experiment several larvae which had well-constructed tubes were 

 removed, tubes and all, to a flat dish. These larvae were keeping a strong current of 

 water flowing through their burrows. After being removed they were placed in shallow 

 water. The tubes were well separated from each other, and the bottom was lightly 

 sprinkled with loose debris similar to that from which the tubes were constructed. 

 After a few hours the larvae ceased to maintain so strong a current and in most cases 

 maintained it only spasmodically. The debris sprinkled over the surface was not 

 disturbed even after being left over night. The current was repeatedly tested and 

 found to be insufficient to furnish any considerable amount of food. 



The tubes were then dissected under a microscope and their inner surfaces were 

 found to be eaten full of rounded holes and enlarged in places. From this it was de- 

 termined that the larva ate away the substance of its burrow from within. While the 

 larva is in such a tube it would probably not be possible to maintain a sufficient current 

 through the burrow to bring in much food on account of the number of openings through 

 its wall. It seems possible, nevertheless, that the current would at times bring in and 



