497 



Lestes type; labium very slender and when folded extending caudad 

 about to the metacoxae ; mental setae five or six ; lateral setae three, 

 two of which are located on the distal segment of the palpus ; marginal 

 mental spinules apparently wanting or few in number and not extend- 

 ing proximad to the base of the expanded portion; the teeth of the 

 mesal margins of the mesal lobe of the proximal segment of the palpi 

 are large and square and the furrow representing the median cleft of 

 the median lobe is conspicuous and extends proximad one-third the 

 length of the expanded portion. 



Thorax slender ; legs very slender, the femora and tibiae with 

 rows of short setae ; femora with subapical rings of brown, the tips 

 of the tibiae and the distal half of the third tarsal segment also dark 

 brown ; wing-cases extending about to the middle of the third abdom- 

 inal segment; lateral keels with strong apical spines on segments 1-9 

 inclusive, the seta at the apex of nine especially long; gills (Fig. 48) 

 very long and slender and of about equal width throughout, the apices 

 bluntly pointed ; ovipositor of the female nearly reaching the apex of 

 segment ten. 



Measurements 



Length 21-30 mm. 



Length of abdomen 17-22 mm. 



Length of gills 13 mm. 



Width of gills 1.25-1.75 mm. 



Length of median lobe 3.3^ mm. 



Width of median lobe 1.5-2 mm. 



The nymph is the longest of any species of Lestes. It is easily 

 recognizable by the slender gills (Fig. 48) and the apical setae of the 

 lateral keels. 



Described from a single exuvium obtained from Dr. E. M. 

 Walker and several specimens in the collection of the Illinois State 

 Laboratory of Natural History from Grass Lake and Havana, 111. ; 

 dates of collection of the specimens from Grass Lake June 23, 24, 1892. 



Adult; Male. — Color, dull metallic green and buff. 



Head dull greenish black or black; median lobe of the labium sub- 

 quadrangular, the median cleft shallow; fixed hook of the palpus black 

 at the apex ; antennae black, the tip of the first segment slightly pale, 

 the second segment twice as long as the first ; postclypeus black, the 

 anteclypeus brown ; labrum pale green ; exposed portions of the mandi- 

 bles, their trochantins, and the genae, pale brown ; front and vertex 

 metallic green. 



