PLECOPTEBA OF XOETH AMEBICA 18.5 



its apex two lobes that may stand out as shown in plate 

 28, fig. 5, or may be folded back so that the edge appears 

 to be uniformly rounded. 



Distribution. — Type locality, "North America." 



West Virginia, Cheat River, June. 



Illinois, Bloomington, June 21, 1894 (C. C. 

 Adams). 



Indiana, no locality. 



Michigan, Ann Arbor, July, 1901. 



Missouri, Columbia (C. R. Crosby). 



Colorado, (Gillette). 



Acroneuria arida Hagen. 



(Plate 16, fig. 5; plate 28, figs. 7, 8; plate 30, fig. 9.) 

 1861. Perla arida Hagen, Syn. Neur. N. Amer., p. 18. 

 1905. Acroneuria valida Banks, Trans. Amer. Ent. Soc, 32:4. 

 1907. Acroneuria arenosa Banks, Cat. Neurop., p. 11. 

 1922. Acroneuria arida Needham and Claassen, Can. Ent., 54:253. 



Length to tip of wings, male, 23 mm. ; female, 28 mm. 

 Expanse, male, 43 mm. ; female, 53 mm. 



Color yellowish. Head wider than prothorax, pale yel- 

 lowish, fuscous in front of the frontal ridge and some- 

 what darker behind the eyes; frontal ridge and lateral 

 tubercles weak, yellow ; antennae dark. Ocelli forming an 

 isosceles triangle, the hind ocelli closer to each other than 

 to the eyes; a black ring inside of the ocelli. Antennae 

 pale brown. Palpi brown. 



Prothorax wider than long, somewhat narrowed be- 

 hind ; light chocolate brown ; a narrow yellow median lon- 

 gitudinal line ; sides of disc quite rugose, often with yel- 

 lowish spots near the lateral margin ; a depressed area 

 near the lateral margin ; front margin evenly rounded, 

 hind margin somewhat angulate, sides straight; angles 

 sharp. Meso- and metathorax brownish with paler marks 

 in front. Legs yellowish, darker above; femora with a 

 wide dark band just before the tip; tarsi dark. Wings 

 subhyaline, veins brown, lighter in the hind wing. Vena- 

 tion as in pi. 16, fig. 5. 



Abdomen yellowish, somewhat darker towards the tip. 

 Tails light yellow, somewhat infuscated towards the tip, 

 covered with moderately long hairs. 



Male. Ninth ventral abdominal segment with a trans- 

 verse oval, polished button. Genital hooks long, cylindri- 

 cal, rather sharply pointed and reaching to or slightly be- 

 yond the middle of segment 10. Segments 9 and 10 above 

 with a patch of spines on each side. 



Female. Subgenital plate produced halfway across seg- 



