108 PROCEEDINGS OF THE ACADEMY OF [Mai'ch, 



To determine whether the larvae breathed through the skin 

 several experiments were conducted. Glass battery jars were 

 filled with pond water and into them were put both larvae with 

 gills and also those from which gills had been removed. A fine 

 gauze was then stretched across the jars about two inches below 

 the water's surface, so that the larvae could not come up to the 

 air. Larvae kept under these conditions, as well as those kept 

 in jars from which the gauze was absent, lived for periods of four 

 to six days — depending of course, upon the amounts of available 

 food substances present in the water. The food question, however, 

 can be eliminated, because both the larvae in the controls, as well 

 as those under experiment, were kept in water obtained from the 

 same pond and were under similar laboratory conditions. 



The same experiment, performed in a slightly different way, 

 gave like results. Larvae, both with and without gills, were put in 

 vials, the ends of which were covered with gauze, and the vials 

 were then dropped into battery jars containing pond water. 

 Larvae put into distilled water in the same manner as above, lived 

 only one to two days — in all probability due to food and osmotic 

 conditions of their environment. 



When the water was previously boiled the length of life of the 

 larvae was greatly reduced — to one and one-half days when under 

 the above conditions. This is doubtless due to lack of food and 

 oxygen in the water used. 



Tracheal System of larva of Enallagma sp., from Primos, Delaware County, 

 Pennsylvania. Larva No. 101. Drawings made by J. H. Bodine, November 

 12, 1915. Fig. 1, dorsal view. Fig. 2, dorsal view of hind end of abdomen 

 with caudal gills. Fig. 3, ventral view. From a transparent specimen. (These 

 are, perhaps, the first complete views, dorsal and ventral, of the tracheal system 

 of an Agrionine larva to be published. A highly magnified drawing of the distal 

 part of a caudal gill in lateral view was published by C. G. Carus as long ago 

 as 1827.— P. P. C.) 



Abbreviations. 



anas, anastomosis of trachese in ab- Imcgt, left median caudal gill trachea. 



dominal segment X. Ivs, left visceral trachea. 



at, antennal trachea. meg, median caudal gill. 



die, transverse trachea connecting ptl, pt^H, ptS, tracheae of 1st, 2nd and 



dorsal and lateral longitudinal 3rd legs, respectively. 



trachea?. rcg, right caudal gill. 



ict, inferior cephalic trachea (to maxilla rcgl, right caudal gill trachea. 



and labium). nit, right dorsal trachea. 



leg, left caudal gill. rU, right lateral trachea. 



Icgt, left caudal gill trachea. rmcgt, right median caudal gill trachea. 



Idt, left dorsal trachea. rvs, right visceral trachea. 



li, labium. ta, thoracic anastomosis. 

 lit, left lateral trachea. 



The Roman numerals denote the numbers of the abdominal segments. 



