Specific Gravity of the Cases of the Larvæ of Limnephilus and Triaenodes (Trichoptera)

Abstract

THE larvæ of many caddis flies build cases which they carry about with them wherever they go. In some recent work on two species of these insects, it was necessary to measure the specific gravity of their cases. The irregular case of Limnephilus was determined by displacement of water in a tube a little larger in diameter than the case. The tube was filled to a datum line with water; some of the water was removed from the tube by a micropipette and the case placed in the remaining water in the tube. The micropipette was now allowed to empty until the tube was refilled to its datum line. Any water still in the pipette equalled the volume of the case. Readings were to the nearest 0.01 ml.