510 



Adults of this species have been taken at Oregon in Ogle County, 

 at Mahomet in Champaign County, and at Muncie and Oakwood in 

 Vermilion County, but the species is not especially abundant in any of 

 these localities. The nymphs are reported by Needham ('03) as living 

 under stones in swift currents and by Kellicott ('99) as living on the 

 piles of docks in Lake Erie. 



Argia skdula (Hagen) 



Nymph. — Unknown. 



Adult; Male. — Color, blue and black. 



Head black and blue, the labium pale blue and buff ; palpi narrow, 

 the second segment dark and shorter than the fixed hook, the cleft of 

 the median lobe obtuse at the base and shallow ; postclypeus pale except 

 a black transverse stripe along the dorsal margin ; anteclypeus, labrum, 

 exposed portions of the mandibles, a transverse area above the clypeus, 

 and a spot latero-cephalad of each antenna blue ; lateral ocelli with small 

 yellow spots laterad of each, the remainder of the front and vertex 

 being black ; postocular blue spots large and contiguous with the mar- 

 gins of the compound eyes ; occiput and postgenae, with the exception 

 of rather narrow black stripes caudad of each postocular spot, yellow- 

 ish buff. 



Thorax : pronotum largely black, the median lobe with large sub- 

 circular spots and the caudal lobe with a pale spot on the extreme 

 lateral angles, blue; proepimera and episterna blue; mesostigmal plates 

 subtriangular, not projecting caudad; dorsal carina of the mesothorax 

 covered by a broad black stripe which also covers about one-half of 

 each mesepisternum and is followed by a broad blue stripe which cov- 

 ers the rest of the mesepisterna ; the blue mesopleural stripe is wider 

 adjacent to the mesostigma and is gradually narrowed caudad; the 

 mesopleural suture is covered by a broad black stripe which also covers 

 most of the mesepimera except the cephalo-ventral shoulders, and is 

 considerably widened adjacent to the wing bases, enclosing a small blue 

 spot ; ventral half of the mesinf raepisterna yellow, the remainder black ; 

 metapleural suture with a narrow black line from wing bases to the 

 metathoracic spiracles ; remainder of the pleura and the postcoxal areas 

 pale blue or buff; legs blue and black, the coxae pale, the trochanters 

 black above, the femora black above and pale below, the front femora, 

 however, with more or less black between the rows of setae ; tibiae black- 

 below, pale above ; tarsi dark brown, the claws bifid at the tip ; wings 

 with twelve to fourteen postnodal cross-veins in the front wing and 

 eleven to twelve in the hind ; M 2 arising between the sixth and seventh 



