531 



Length of abdomen, S 26 mm. 



Length of abdomen, S 25 mm. 



Length of hind wings, $ 19 mm. 



Length of hind wings, 9 19 mm. 



Width of hind wings, 3 4 mm. 



Width of hind wings, 9 4 mm. 



An inhabitant of the lake regions of Illinois, the nymphs prefer- 

 ring floating vegetation or rank growth along the banks of ponds or 

 lakes of considerable size, though they are occasionally to be en- 

 countered in the larger and clearer streams. 



The color of the recently emerged adult is buff or cream-color and 

 biack, and the blue is much slower in appearing than in other species. 



Enai.l.a.gma civile (Hagen) 



Nymph. — Color, green or buff. 



Head about twice as broad as long, the caudo-lateral angles not 

 projecting caudad or laterad, but armed with short setae ; antennae 

 with the third segment longest, the first shorter than the second, the 

 first two segments and the proximal portion of the third dark brown, 

 the remainder of the third and the distal segments pale; labium ex- 

 lending just caudad of the first pair of coxae, the median lobe with 

 three or four mental setae, the labial palpi with five or six lateral setae 

 and a row of seven or eight small setae on the margin of the median 

 lobe. 



Thorax pale buff' or green; legs very pale, the preapical femoral 

 rings indistinct, the femora w-ith a dorsal and lateral row of setae and 

 scales near the tips: metathoracic wing-cases extending caudad to the 

 middle of the fourth abdominal segment. 



Abdomen pale buff or green, frequently with an indefinite darker 

 stripe on the dorsum of segments 3-7, the cuticle sparsely provided 

 with minute setae, which are usually lacking on the venter of the 

 cephalic segments ; dorsum of two, three, and four with long hair-like 

 setae ; lateral keels well developed and setose, the first w'ithout setae, 

 the second with a row of about eleven, the third with twelve, the 

 fourth with sixteen, fifth with eighteen to tw-enty, sixth with fifteen to 

 sixteen, seventh with twelve to fourteen, and the eighth with a straight 

 row of about nine setae; gills (Fig. 75) lanceolate, colorless and 

 usually without pigment except in the smaller tracheae, the margins 

 very transparent ; dorsal marginal setae of the median gill extending 

 less than half the length of the gill from the base, and composed of 

 more than twenty setae ; ventral row of the lateral gills slightly longer 



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