Clarke.] 68 [May 24, 



loosely attached to the stone by its edges, and without any bot- 

 tom. It may be composed entirely of sand, or of bits of plants, 

 or both combined. 



The supporting framework of the net is always formed of veg- 

 etable bits, and is sometimes a simple arch, sometimes a complete 

 ring, and sometimes a short cylinder. It is occasionally stayed 

 or held in position by silken cords stretching from it to suitable 

 points on the stone. It is stiff enough to stand erect even when 

 removed from the water. When it is in the shape of a cylinder 

 or broad arch, the net is always stretched across that end of it 

 which is down stream, and the entrance usually opens under the 

 shelter of the arch. 



The case of the pupa (fig. 2) is more strongly built than that of 

 the larva. It is symmeti ical and oblong, over half an inch long, 

 composed of coarse sand-grains or tiny stones, 

 and firmly attached to the foundation stone by 

 its edges. Across the bottom, resting on the 

 stone, is a silken web. At each end, nearly con- 

 cealed by the little stones, is a grating which 

 insures a fresh current of water through the case. 



The larvae are strong little creatures, with the body grayish, 

 and the head, thorax and short legs dark brown. The body is 

 somewhat curved, and copious tufted gills hang from the under 

 side. Dr. Hagen will give a detailed description of them at 

 another opportunity. 



In a stream in Brookline, Mass., are large communities of these 

 larvae. The stones in the stream are covered with mud, leaves, 

 sticks and rubbish. Looking down upon these stones, quantities 

 of dark holes can be seen, facing the current, often a row of them 

 side by side, stretching abliquely across the stone. Removing a 

 mass of the rubbish with the hand, the delicate net can be seen 

 across each hole, supported by its framework of vegetable bits. 

 Sometimes a stick, which has fallen into the brook, has a row of 

 cases and nets built upon it. Often a stone will have a row of 

 them side by side along one edge, or there may be only a few of 

 these structures scattered separately upon its surface. 



I have always found them where the current is very swift, and 

 if the stones with the cases and larvae are placed in standing 



