562 



Genus Amphiagriox Selys 



Tlie nymph of the only species of the genus known to occur 

 in lUinois is easily distinguished from other genera by means of the 

 projecting caudo-lateral angles of the head. The gills are without 

 cuticular pigment and are decidedly ovate in shape. 



The adults are red or brown in color. The stigma of both front 

 and hind wings is turned obliiiuely to the long axis of the wing and 

 the width is much greater than its length. The eighth sternum of 

 the female possesses a long seta, and the sternites at the base of the 

 cephalic pair of gonapophyses are small but visil)lc with moderate 

 magnification. The superior anal appendages of the male are much 

 sliorter than the inferiors and tlie paramcrcs of the ninth sternum do 

 not reach the apex. 



Amphiagriox s.mcium (Burmeister) 



Nympli.-— Color, dark brown. 



Head pentagonal and characterized by having the caudo-lateral 

 angles projecting strongly and forming a short blunt tubercle ; an- 

 tennae composed of seven segments, the distal segments being short 

 and similar to those of the nymphs of the genus Argia ; laliium broad, 

 when folded extending to the metacoxae, the median lobe with three 

 or four mental setae and six lateral setae, and the margins of the 

 median lobe with ten to twelve setae. 



Thora.x i)rown; legs without brown rings ami unifcirm in color; 

 femora indi.stinctly carinate ; tibiae with rather closely set slender 

 setae; wing-cases extending caudad to the fourth or fifth abdominal 

 segment. 



Abdomen thickset, the lateral keels absent or feebly developed 

 arid without setae; ovipositor of the female nearly reaching the apex 

 of the tenth segment in full-grown nymphs; caudal gills (Fig. 59) 

 transparent, ovate-lanceolate, the apices gradually narrowed to a sharp 

 point; margins of the gills setose fnmi the jjroximal to the distal end, 

 the setae placed closely together and increasing in length towards the 

 apices; tracheal trunks sometimes subdividing and forming a number 

 of large branches near the proximal fourth of the gill. 



Mcasurcmaiis 



Length 11-14 mm. 



Length of abdomen 7-10 mm. 



Length of gills 4.5 mm. 



Width of gills 1.5 mm. 



