92 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [Bull. 



two-thirds as long as broad ; palpi with simple hooks besides the 

 movable distal segment. 



Thorax : dark brown ; legs with coxae and trochanters dark, 

 the femora with fuscous bases and apices and usually two broad 

 rings in addition ; tibiae dark brown at base and apex, and a ring 

 just proximad of the middle; tarsi dark. 



Abdomen : dark brown with a pale mesal stripe ; lateral keels 

 feebly developed and without or with minute setae; gills ovate, 

 uniform dark brown, or sometimes having a V-shaped mark on 

 each near the apex ; ovipositor of the female extending to apex 

 of the tenth abdominal segment or beyond. 



Measurements: length (with gills), 17 mm.; length of abdo- 

 men, 7 mm. ; length of gills, 4.5-5 mm. ; width of gills, 2-2.5 ^"^- ' 

 length of median lobe, 1-2 mm. 



Adult, male. — Color dark brown or purple. 



Head : antennae with the basal segment and sometimes the 

 proximal end of the second segment buff, remainder black ; clypeus 

 and labrum pale brown, the front, vertex and postocular regions 

 also largely pale but becoming violet with age, the black confined 

 to a broad transverse band embracing the lateral ocelli, a T-shaped 

 mark ventrad of the median ocellus and narrow lines extending 

 from the ends of the transverse band to the compound eyes and 

 to the caudal margins of the head ; caudo-dorsal margins of the 

 head with a black line. 



Thorax : brown or violet, and black, median lobe of the prono- 

 tum with large brown or purple spots ; dorsal carina black, the 

 stripe on each side about one-third the width of the anepisterna ; 

 a black stripe present just below the mesopleural suture, the stripe 

 contiguous with the cephalic half of the longitudinal part of 

 suture ; metapleural suture lined with black ; metepimera and 

 postcoxal areas buff, legs striped, tarsi and claws black; wings 

 clear, the stigma surmounting a single cell or less ; postnodal 

 cross-veins of the front wing 11-15, and M2 arising between the 

 fifth and seventh of these. 



Abdomen : purple and black or brown and black ; basal half 

 of first tergum black ; second tergum with lateral spots extending 

 from cephalic margin nearly to apex of the segment ; 3 and 4 

 brown or purple, with exception of a caudo-lateral dark spot on 

 either side ; terga 5 and 6 with a dark apical ring and sometimes 

 narrow lateral black stripes; 7 black, 8, 9 and 10 blue on dorsum, 

 black on lateral surfaces; anal appendages (Fig. 12, No. 16) 

 consisting of short blunt superiors and longer inferiors. 



Female. — Color dark brown or dull violet. 



Head : similar to the male. 



Thorax: mesostigmal plates with rounded lobes on the caudo- 

 mesal angles (Fig. 11, No. 16) ; abdomen with more black than 

 the male; terga 2-9 with dorso-lateral dark stripes which are 



