. Bulletin. Natural history; Natural history. 56 Illinois Natl'rai. History Survey Bulletin Vol. 26, Art. 1 for example, has only a few dozen ailults but hundreds of nymphs. Ill the Nearctic rej;ion. the family Ephem- ercUidae includes one jienus. Ephtnuitlla. 13. Walsh ;hfmfrtUa Walsh (1862:377). Drunrlla Nccdham (1905:42). (:/iilono/>/iora Htngtssim (1908:243; 1909:6). Torlryti Lestage (1917:366). Timf>anoga Necdham (1927:108). Eatotiflla Necdham (1927:108). This nenus now includes more than 80 Nearctic species, only 11 of which have, so far, been taken in Illinois.
. Bulletin. Natural history; Natural history. 56 Illinois Natl'rai. History Survey Bulletin Vol. 26, Art. 1 for example, has only a few dozen ailults but hundreds of nymphs. Ill the Nearctic rej;ion. the family Ephem- ercUidae includes one jienus. Ephtnuitlla. 13. Walsh ;hfmfrtUa Walsh (1862:377). Drunrlla Nccdham (1905:42). (:/iilono/>/iora Htngtssim (1908:243; 1909:6). Torlryti Lestage (1917:366). Timf>anoga Necdham (1927:108). Eatotiflla Necdham (1927:108). This nenus now includes more than 80 Nearctic species, only 11 of which have, so far, been taken in Illinois. Quite a few more species of Kt^lu iiuii ll<i niij^ht, however, basal three of which are short and approxi- mately equal in length; the apical segment is usually as long as the basal three com- bined. P^ach arm of the male genital forceps has three segments, the basal one short, broad, and usually indistinctly set off from the distal ones; the second segment is long and somewhat bowed; and the third segment is usually minute, although it is fairly long in a few species. The penis lobes invariably are fused at the base on the meson; in most species, this mesal fusing extends almost to the tips of the penis lobes. There are three long caudal filaments. The nymphs, figs. 172 and 17.^, are more or less flattened dorsovcntrally. In each, the. Fig. 115.—Ephrmerrlla argo, head of adult male, anterior aspect. Fig. 116.—Ephemerrlla lutulenta, hind wing of adult. Fig. 117.—Kphemerella ora, head of aduit male, anterior aspect. eventually be found to occur in the smaller streams in the northern tier of Illinois counties. For that reason, a number of extralimital, northern species of Ephemerella have been included in the keys and discus- sions given below. In each fore wing of the Ephemerella adults, the costal crossveins are entirely wanting or a few apical ones are very weakly indicated, the stigmatic crossveins are weak and usually slightly anastomosed, and all other crossveins a
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