. Bulletin. Natural history; Natural history. 190 Illinois Natural History Survey Bulletin Vol. 26, Art. 1. Fig. 385. — Heptagenia perfida, mature nymph, dorsal aspect. orange shading. Thorax dull brown dor- sally, light yellow ventrally. Abdomen dull brown dorsally, darker at posterior margins of tergites, sternites light yellow; posterior margin of terminal sternite produced and truncate on meson; caudal filaments light yellow, basal articulations tan. Nymph.—Fig. 385. Length of body 6-8 mm. Head slightly wider than thorax, dor- sal side of head brown, with a pair of sub- mesal, white spots
. Bulletin. Natural history; Natural history. 190 Illinois Natural History Survey Bulletin Vol. 26, Art. 1. Fig. 385. — Heptagenia perfida, mature nymph, dorsal aspect. orange shading. Thorax dull brown dor- sally, light yellow ventrally. Abdomen dull brown dorsally, darker at posterior margins of tergites, sternites light yellow; posterior margin of terminal sternite produced and truncate on meson; caudal filaments light yellow, basal articulations tan. Nymph.—Fig. 385. Length of body 6-8 mm. Head slightly wider than thorax, dor- sal side of head brown, with a pair of sub- mesal, white spots on anterior margin, a second small pair of white spots just pos- terior to these, three fairly large spots be- tween eyes and posterior to antennal bases, and a white streak extending from antero- lateral angle of each compound eye to mar- gin of head. Thorax brown, marked with obscure, paler spots; each tarsal claw with basal tooth virtually wanting and only three to five ventral denticles. Dorsum of abdo- men brown, tergites 1-7 each with a pair of submedian, white streaks, usually a pair of small, white dots at posterior margin lateral to submedian streaks, and a pair of posterolateral, white, triangular marks; median area of tergites 8 and 9 each with a large, white blotch; filamentous tuft ab- sent in gills borne by seventh segment, tuft borne by sixth pair of gills reduced in size; abdominal sternites each with a slightly irregular, brown crossband at anterior mar- gin; caudal filaments tan, unmarked. Known from Illinois and Ontario. Illinois Records.—Alto Pass: May 31, 1940, B. D. Burks, 2 $ ; Union Springs Church, May 12, 1939, Burks & Riegel, 2 $ ; June 1, 1940, B. D. Burks, 1 5 , 1 N May 3, 1946, Burks & Sanderson, 2^,1$ May 15, 1946, Mohr & Burks, 2 5,2$ branch of Clear Creek, May 19, 1946, Mohr & Burks, 2$, 15. Cora: May 3, 1946, Burks & Sanderson, 1^, 1$. Eddyville: Lusk Creek, June 6, 1946, Mohr & Burks, \S. Golconda: May 13, 1939, Bu
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