504 



Abdomen half as broad as long, dark brown in color, tlie dorsum 

 with a pale median stri])e which widens noticeably on segments eight, 

 nine, and ten; gills (Fig. 67) elliptical, smoky, frequently possessing 

 one or two pale transverse bands and usually with a number of 

 coarse spots of pigment ; apices of the gills bluntly pointed, the margins 

 hairy, but without heavy setae; ovipositor of the female extending to 

 the apex of segment ten. 



Measurements 



Length 14 mm. 



Length of abdomen 8 mm. 



Length of gills 6 mm. 



Width of gills 3 mm. 



Length of metathoraeic wing-cases. . .4..5 mm. 



Length of median lobe 3 mm. 



Width of median lobe 1-2 mm 



Adult; Male. — Color, light blue (light amparo blue), or bufif 

 (warm buff) and black. 



Head : exposed portions of tlie mouth-parts buff or light blue, 

 the median lobe of the labium subtriangular, the cleft shallow and 

 obtuse at the proximal end; proximal segment of the labial palpus 

 about three times as long as the distal segment ; fi.xed hook only 

 slightlv longer than the distal segment, black; distal segment black; 

 antennae black with the exception of the first segment which has a 

 pale lateral stripe ; clypeus and labrum. genal region, exposed portions 

 of the mandil)les, and the front dorsatl t(i tlie level of the lateral ocelli, 

 blue; vertex black; ocellar area black, the latter sending a black line 

 ventrad to each antenna ; postocular spots present, circular, blue or 

 brown ; occiput and postgenae yellow with the exception of small black 

 spots on the postgenae, near the ventral margins of the compound 

 eyes. 



Thorax light blue or buff, black, and sulphur yellow ; prothorax 

 black and blue ; caudal lobe of the pronotum l)lack. median lobes with 

 circular blue spots; noto-epimeral suture indistinct; proepimera blue 

 or buff, the dorsal margins black ; mesopleura and metapleura blue 

 or olive-buff, and without black markings except a short stripe covering 

 the dorsal half of the mesinfraepisternum. which extends caudad on 

 the mesepimeron for about one-fifth of the length of that sclerite; 

 postcoxal areas buff or yellow ; legs striped with black and yellow, a 

 stripe on each side of the femoral carinae and one on each tibia en- 

 closing the cephalo-ventral row of setae; tarsi black, the second and 



