542 



Enaixagma exsulans (Hagen) 



Nymph. — Color, dark brown or greenish. 



Head slightly broader than long, the caudo-lateral angles pro- 

 jecting caudad and provided with heavy setae ; second antennal seg- 

 ment shorter than the first, the first two darker than the remaining 

 ones and pilose; labium extending just caudad of the procoxae, mental 

 setae three in number ; lateral setae four or five, and six or seven 

 marginal setae on the median lobe. 



Thorax : legs with a few hair-like setae, the femora each with a 

 preapical ring of brown and the tibiae with the usual scales at the tip; 

 apices of the third tarsal segments and the apices of the claws dark ; 

 metathoracic wing-cases extending caudad to the fourth abdominal 

 segment. 



Abdomen slender, the cuticle provided with minute setae and 

 minute brown spots; lateral keels well developed on segments 1-8, 

 the keels on segments 4-8 and the lateral apex of segment nine with 

 small groups of two, to five setae; gills (Figs. 53, yy, 77^) broadly 

 lanceolate, broadest beyond the middle, usually heavily pigmented on 

 the proximal two-thirds, the area of infuscation being followed by 

 two large clear spots on each side of the axis, the distal end of the 

 gill being dark, the extreme tip white ; marginal setae of the median 

 gill consisting of a dorsal row extending from the base to the light 

 spots, or nearly two-thirds the length of the gills, and ventral marginal 

 setae of the lateral gills of similar extent ; apical margins of all gills 

 hairy; smaller tracheae forming alga-like patches; ovipositor extend- 

 ing to the middle of the tenth abdominal segment. 



Measurements 



Length 12-13.5 mm. 



Length of abdomen 9-10 mm. 



Length of gills 5.5-7 mm. 



Width of gills 1.8-2 mm. 



Length of median lobe 2 mm. 



Width of median lobe 6-1.8 mm. 



Adult; Male. — Color, pale blue, black, and brown. 



Head pale blue and black ; median lobe of the labium buff, sub- 

 triangular, the cleft obtuse at the base ; antennae entirely black ; post- 

 clypeus black, shining, the anteclypeus pale and the labrum with a 

 transverse black stripe on the dorsal margin ; exposed portions of the 

 mandibles, their trochantins, genae, and a transverse area between 



