AQUATIC INSECTS IX NEW YORK STATE 237 



N'ymphs 



a Labium -witli no raptorial setae on the mentum 

 ■within; gills broad, thick, dark colored, 

 oval or oblong in shape and obtuse at 



apex Argia 



aa Labium with mental setae; gills thinner, more 

 pointed and narrower [pi. 15] 

 & Hind angles of the head strongly angulate 

 c Gills widest beyond the middle; body slender; 



head half as long as wide Chromagrion 



cc Gills widest across the middle; body stouter; 



head nearly as long as wide Amphiagrion 



66 Hind angles of the head rounded 



d Labium with one mental seta (and a rudimen- 

 tary second one) each side; antennae six- 

 jointed; lateral lobe of the labium with 

 [ the distal end above the end hook hardly 



denticulated Nehallennia 



dd Labium with three to five mental setae each 

 side (one may be smaller than the others), 

 and end of lateral lobe denticulated dis- 

 tinctly; antennae seven -jointed (with the 

 possible exception of E. a n t e n - 

 i n a t u m ) 



e Gills more than haJf as long as the abdo- 

 men, lanceolate; third segment of anten- 

 nae less than a third longer than the 

 , second 



f Labium with four to six lateral setae, gen- 

 erally with five, and with three (rarely 

 four) mental setae each side; gills often 



with a definite color pattern Enallagma 



ff Labium with five or six lateral setae, and 

 with four mental setae each side; gills 



generally with no distinct pattern I s c h n u r a 



ee Gills less than half as long as the abdo- 

 men, narrower and with a long tapering 

 point; third segment of antenna more 

 than a third longer than the second Anomalagrion 



ARGIA 



This is another large genus whose species are nearly all 

 American, and whose habitat is chiefly tropical or subtropical. 

 In New York State are recorded five species, and a sixth is 

 regional and is included in this list. Of these six, four have 

 been bred, and their nymphs are here described for the first 

 time. 



