120 TERTIARY INSECTS OF NORTH AMERICA. 



EPHEMERA Linn^. 



Tlie species known only in the inimatnre stages may be distinguished 

 as follows : 



Taile of tlie species of Ejiliemera. 



Outer caudal setie friuged on l)otb sides. Middle seta as loug as the outer setiT'. 



SetiB very much more widely tViuged iu the middle than toward either end; dorsal abdominal 



markings consisting of light blotches on a dark ground 1. E. tabijica. 



SetiB only a little more widely fiinged iu the middle than toward the base or tip; dorsal abdom- 

 inal markings consisting of ligbt lines on a dark ground 3. E. macilevta. 



Outer caudal setse fringed on the inner side only, and very much more broadly in the middle than 



near the base or tip. Middle seta shorter than the outer setae 2. E. immobilis. 



Setae of equal length and naked, or not noticeably fringed. 



Large species. Head less than half the width of thorax; dorsal abdominal markings of light 



lines 4. E. puviicosa. 



Small species. Head considerably mors than half as wide as the thorax ; no dorsal abdominal 

 marking 5. £. inlerempta. 



1. Ephemeea tabifica. 



Pupa. — This species differs somewhat in form from tlie otlier larger 

 types, the abdomen being very nearly of equal size throughout and the 

 thorax nearly twice as broad as it, while anteriorly the whole body tapers 

 regularly, as in tlie succeeding species. The head is rounded quadrate, 

 about half the width of the thorax. The legs are slenderer than in the 

 succeeding species and short, the front pair no longer than the width of the 

 thorax, the hind pair longer, being as long as the head and thorax togetlier. 

 The wing pads are blackish, about three times as long as broad, reniform 

 in shape, the inner margin bent in the middle, and the basal halves of the 

 inner margin of the two wings meeting to form an angle slightly less than 

 a right angle, the apical half tapering to a rounded apex. The abdomen 

 is long and slender, the apical joint more than half as broad as the basal, 

 the dorsal surface blotched with large quadrate patches of lighter color 

 than the gi-ound, sometimes central, sometimes anterior and transverse, 

 divided by a median line. The three caudal setas are slender, less than 

 half as long as the abdomen, equal, very broadly fringed on either side in 

 the middle. 



Length of body exclusive of sets, 25°™ ; breadth of thorax, 4.5""' ; 

 of middle of abdomen, 2.6°"" ; length of wing pads, 4.5"™ ; of front legs, 

 4"" ; of hind legs, 8°'™ ; of setfe, 7°'"'. 



Florissant. One specimen, No. 13238. 



