52 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [BuU. 



Abdomen : lateral keels of segments 6-8, with not more than 6-7 

 spinules, that of the first segment usually without any; cuticle of 

 the abdomen with small whitish spots on a darker background; 

 gills broader beyond the middle, the lateral gills with 10-12 black 

 spots on the margins and sometimes a distinct arcuate cross-band 

 beyond the middle ; tracheal branches more numerous beyond the 

 middle ; marginal spines of lateral gills well separated, the proxi- 

 mal ventral row of heavy spines extending beyond the middle of 

 the lateral gills ; ovipositor usually extending beyond the apex of 

 the tenth segment. 



Measurements: length, lo-ii mm.; length of abdomen, 7-8 

 mm. ; length of gills, 4-4.5 mm. ; width of gills, i mm. ; length 

 of median lobe, i. 5-1.7 mm. 



Adult, male, — Color bright metallic green, yellow, and some- 

 times pale blue. 



Head : metallic green, pale below ; mouth-parts, ventral half or 

 two-thirds of labruni, genae and front to clypeo-frontal suture, 

 yellow ; dorsal half or third of labrum usually black ; postclypeus 

 black or green ; remainder of head including vertex, occiput, and 

 postgenae mostly metallic green ; second segment of the antennae 

 with a pale ring at middle. 



Thorax : pronotum green, propleura pale ; mesothorax with 

 black dorsal carina ; episterna green except the ventral third of 

 the katepisterna and a pale line on its dorsal border ; mesepimera 

 mostly green, their cephalic shoulders pale; metapleura pale 

 yellow, except for the caudo-dorsal angles of the episterna and a 

 small black spot on the metapleural suture near the wing-bases ; 

 postcoxal areas yellow ; legs striped but mostly pale yellow, the 

 femora all with a distinct dorsal vitta, the tibiae also with a nar- 

 rower stripe above but not usually extending the full length of 

 the segment ; tarsi and claws pale except at their apices ; wings 

 with 9-11 postnodal cross-veins in the front wing, M2 arising 

 usually between the fourth and fifth of these in the front wing 

 and between the third and fourth in the hind. 



Abdomen : metallic green above the lateral margins of the 

 terga, pale yellow or blue; dorsum of 1-8 green above, usually 

 blue on sides of 2 and 8. the remaining terga usually with yellow 

 margins, terga 9 and 10 blue with green basal, somewhat trian- 

 gular areas on each side of the meson ; anal appendages mostly 

 pale, the superiors small, the inferiors toothed at their apices. 



Female. — Color metallic green or bronze and yellow. 



Thorax: pronotum (Fig. 11, No. 17) differing from the 

 male in having the caudal lobe emarginate on each side of the 

 meson, the piece being trilobed in consequence ; the mesostigmal 

 plates have the mesal margins strongly elevated. 



Abdomen : ninth tergum green above with an apical blue or 

 brown triangle and blue lateral margins; tergum 10 blue, with 



