294 PROCEEDINGS OF THE NATION AL MUSEUM. vol.49. 



ill tliis \nolct and brown stage with segments 8/9, and 10 blue, which 

 I believe is the usual breeding color. 



Nymph. — (figs. 37, 38, 71-76). — A short nymph with very dark 

 color, and color pattern very obscure except the broad wliite stripe 

 down the middorsal line of the abdomen. Caudal gills small and legs 

 weak. 



Total length, not including gills, 12 mm.; length of abdomen 

 without gills, 7; length of gills, 3; width of head, 3.6; length of liind 

 leg, 7.5. Head broader than long, the posterior margin almost 

 straight, being very sHghtly emarginate between the postocular lobes. 

 Antennae (see fig. 76) short, their length less than length of head; 

 base and first two joints black, the four distal joints white with 

 obscure darker rings. (These markings fade very soon in alcohol.) 

 Men turn short and broad, almost square; anterior margin of hgula 

 slightly convex. Four raptorial setae on each lateral lobe, the 

 anterior setae as long as the end hook, the others successively shorter. 

 The end hook is not separated by a notch from the inner margin as 

 in emma. (See figs. 71 and 71a.) 



Prothorax twice as broad as long. Ridge around posterior edge 

 not prominent. Dorsal surface flat except a minute semicircular 

 depression on the anterior portion. Femora of first pair of legs two- 

 thirds as long as femora of second pair. Tibiae of first pair almost 

 as long as tibiae of second pair. 



Mesothorax and metathorax equal and either sHghtly longer than 

 the prothorax. A deep concavity extending from the anterior point 

 of the anterior wing pads to the mesinfraepisternum. A short tubercle 

 between the upper edge of the mesinfraepisternum and the posterior 

 edge of the prothorax. Posterior wing pads extending to the pos- 

 terior edge of abdominal segment 3. Femora of last pair of legs 

 extending to middle of segment 4. 



Abdomen widest in segments 4 and 5 wliich are only shghtly less 

 wade than thorax. A low lateral keel on segments 1-7 (inconspicuous 

 on 7). Abdomen very dark, with a very conspicuous white mid- 

 dorsal stripe, which is narrow cephalad and widens caudad until it 

 is widest on segment 9 (all other abdominal markings obscure). The 

 middorsal stripe bordered by dark. A light irregular stripe associated 

 with each lateral keel, which is edged above and below by darker. 

 The lateral gills less conspicuously spoon-shaped than in the emma 

 nymph, the prominent rib making them more roof shaped. 



In the male the two points on the abdominal segment 9 are shorter 

 and more pyramidal than in the emma male. (See figs. 74, 75.) 



Female with the two outer or ventral members of the ovipositor 

 as long or longer than the upper or inner pair (except in immature 

 larvae). The genital valves roughened on the distal half of the ven- 

 tral edge, any teeth being hidden by long hairs. The posterior tips 



