EPHEMERINiE. 533 



first joint broad : prothorax slightly conical, not broader than long; 

 borders and dorsal stripe testaceous : mesothorax and metathorax 

 each as large as the prothorax ; mesothorax partly testaceous : ab- 

 domen linear, not broader or longer than the thorax, with a short, 

 broad, testaceous stripe on the disk : legs testaceous ; femora with 

 piceous streaks. Length of the body b\ lines. 



The broader head of this species and the shape of its prothorax 

 distinguish it from O. Brasiliensis. 



a. Brazil. From Mr. Stevens' collection. 



Sub-order 5. EPHEMERIN.E. 



Partes oris obliterate, subnullae. Abdominis apex bi- vel tri- 

 setus. Tarsi 4-5-articulati. Alae duo vel quatuor, inasquales, 

 homonomae, membranaceae, venis transversis plurimis. Larva? 

 aquaticae, branchiopneustae, nudas. 



Ephemerinae, Latr. ; Pictet; Blanchard. 



Ephemera, Linn. ; Fabr. ; Deg. ; Barb. ; Gmel. ; Berk. ; Steiv. ; 



Turt. ; Panz. 

 Agnatha, Cuvier. 



Ephemeridas, Leach ; Steph. ; Curt. ; Westw. 

 Bioraorphotica, p., Westw. 

 Arkiptera, p., Bridle ; Delaporte. 

 Ephemerina, Newman. 



" Antennae very short, 3-jointed ; terminal joint longest, and a 

 mere seta. Ocelli three. Mouth and prothorax atrophied. Abdo- 

 men terminating in long caudal multiarticulate setae. Legs simple; 

 fore-legs longer and porrected in the males. Wings much reticu- 

 lated with veins, very unequal in size, the fore-wings being ample, 

 the hind small, and sometimes totally wanting ; when at rest they 

 are erect and meet vertically over the back. Larva. — Aquatic, 

 breathes by means of external gills, which also serve as organs of 

 natatory locomotion. Antennae long, filiform, multiarticulate. 

 Mandibles corneous, small, feeble. Setae long, filiform, multiarti- 

 culate. Legs long and strong. Frequents the bottom of ponds, 

 and especially of running streams, secretes itself under stones, and 

 appears to feed on the decomposing organic matter which mingles 

 so largely in the sediment of all waters. Pupa. — Similar to the 



