515 



Argia violacea (Hagen) 



Nymph. — Color, very dark brown. 



Head pentagonal, the caudo-lateral angles nearly rectangular and 

 provided with a few weak setae ; antennal segments all dark except the 

 proximal one, which is light in color ; third segment longest and the 

 second longer than the first ; labium short and broad, the width about 

 two-thirds the length; lateral setae two or three. 



Thorax short, dark brown, with a black stripe on each side ; legs 

 with dark coxae and trochanters, a narrow proximal ring on each 

 femur which is followed by two broad brownish rings, the three divid- 

 ing the femur into fourths; tibiae with narrow proximal rings and 

 rings of similar size shortly before the middle, the apices dark; tarsi 

 dark, though not as dark as the rings of the femora and tibiae. 



Abdomen dark brown with a paler mesal stripe on the dorso- 

 meson ; lateral keels feebly developed and without setae on their lateral 

 margins; gills ovate, more than half as broad as long, uniform brown 

 or sometimes having paler V-shaped marks near the apices, the mar- 

 gins thickly covered with setae arranged irregularly ; ovipositor of the 

 female with sharply pointed lateral valves which extend beyond the 



tenth abdominal segment. 



Measurements 



Length 17 mm. 



Length of abdomen 7 mm. 



Length of gills 4.5 mm. 



Width of gills 2.5 mm. 



Length of metathoraeic wing-cases ... 5 mm. 



Length of median lobe 3 mm. 



Width of median lobe 1.25-2 mm. 



Adult; Male. — Color, dark brown or purple (Matthew's purple). 



Head : median lobe of the labium pale ; distal segment of the labial 

 palpi black at the tip; antennae black or dark brown except the basal 

 segment, which is buff ; clypeus and labrum pale brown, the front, ver- 

 tex, and postocular regions also largely pale but becoming violet with 

 age, the black confined to a broad transverse band embracing the two 

 lateral ocelli, a T-shaped mark ventrad of the median ocellus, and nar- 

 row lines extending from the ends of the transverse band to the com- 

 pound eyes and to the caudal margins of the head ; caudo-dorsal mar- 

 gins of the head with a black line; occipital and postgenal regions 

 largely yellow ; compound eyes, slate-gray. 



