490 



Abdomen: cuticle provided with minute setae and somewhat 

 heavily pigmented with brown ; lateral keels with heavy apical setae on 

 segments 5-9 and with about nine smaller setae along the keels to their 

 bases; sterna with a double row of median spots, two to each segment ; 

 segment ten hairy beneath; gills similar to those of forcipatus, with 

 a row of short setae on both margins, the extreme tips being usually 

 free ; the portions of the eleventh segment proximad of the lateral gills 

 bear five or six small setae on the ventral surface ; the pigmentation 

 of the gills is usually brownish, though frequently black, but the gill 

 is not as a rule as black as the gill of forcipatus; female ovipositor ex- 

 tending to the apex of the tenth abdominal segment. 



Measurements 



Length 22 mm. 



Length of abdomen 17 mm. 



Length of gills 9.5 mm. 



Width of gills 2.3 mm. 



Length of median lobe 4 mm. 



Width of median lobe 5-2.0 mm. 



Adult; Male. — Color, dark brown to black, and sulphur-yellow. 



Head brown and yellow ; labium pale, the median lobe subquad- 

 rangular, with a shallow cleft and darker stripe extending proximad 

 to the base ; palpi rather short ; antennae entirely brown, the first seg- 

 ment much shorter than the second, and the third and fourth much 

 longer than the first two together; postclypeus dark brown, shining, 

 the anteclypeus, labrum, exposed portions of the mandibles, their 

 trochantins, and the genae, shining yellow; front and vertex, dull 

 brown, nearly black, the preocellar furrow very deep and extending 

 laterad nearly to the bases of the antennae ; occiput and postgenae black, 

 pollinose with age. 



Thorax brown and yellowish; pronotum yellowish buff, the ce- 

 phalic lobe with a large median brown spot, the median lobes each with 

 an irregular H-shaped mark which covers a large portion of the lobe 

 in the older specimens; caudal lobe blackish brown, the caudo-lateral 

 margins pale; supraepisterna of the mesothorax with a broad, brown, 

 longitudinal stripe from cephalic to caudal margins, covering about 

 three-fourths of the sclerites, the lateral margins of the stripe irregular; 

 mesopleural suture covered by a broad yellow stripe which is widest 

 cephalad, narrowed near the wing bases, and becomes bluish with age ; 

 mesepimera with longitudinal median brown stripes extending from 

 near the caudal margin to the cephalic shoulder, widened considerably 



