ephemerid.t:. 



5i95 



two abdominal set<T, while the four wings are provided with 

 numerous cross-veins. The ej-es are simple, and in the males 

 of large size and placed very near each other. Baetis inter- 

 punctata Say is a yellowish white species tinged with green, 

 Avith L arcuate black line on the front, and a lateral black 

 point, Avhile the prothorax has one black stripe on the side. 



The singular genus Bcetisca is very thick-bodied, and differs 

 from the other Ephemerids in the fifth abdominal joints being 

 twice as long as any of the others. 

 The pupa (Fig. 576, i ; a, lateral 

 tooth ; II, antenna ; iii, section of 

 tlie abdomen, the numerals indicat- 

 ing the segments ; a, branchiae, 

 above which is a flap, b) "differs," 

 according to Walsh, "from all de- 

 scribed Ephemerinous pupte in the 

 antennae being eig^it-jointed or there- 

 abouts, not multiai'ticulate, and also 

 in the branchijB being internal and 

 not used for locomotive purposes, 

 and from all larvjE and pupae, and indeed from all known 

 hexapod insects in an}^ of their states, in the pro-, meso- and 

 metanotum being connate and confluent, and extending over 

 one-half of the abdomen in the form of a large, dilated, convex 

 carapace, or shield, thus giving the in- 

 sect a very Crustacean appearance." 

 The larva, early in its life, has rudi- 

 mentary wings, as in many grasshoppers, 

 but in the pupa state they are not 

 present. 



Near Baetis comes Potamanthvs, which 

 has three caudal setae and four wings 

 provided w^ith numerous cross- veins ; the 

 eyes in the males are double, large and , ^'S- ^"■ 

 approximate. The Potamanthus aqndns of Say is black, with 

 a broad dorsal stripe and a lateral impressed line on each side 

 of the thorax. P. marginatus Zetterstedt (Fig. 577), a boreal 

 European species, we have found in abundance in Labrador fly- 

 ing over pools in July. 



Fig. 576. 



