THE INSECTS. 341 



Stephen defines Cloeon : Head small, transverse ; eyes 

 moderate, remote lateral ; thorax ovate ; wings, two, elon- 

 gate, rounded at the apex with numerous longitudinal ner- 

 vures, and a few transverse ones ; posterior pair wanting ; 

 abdomen rather long, attenuated at apex, with two more or 

 less elongated setae ; legs slender, anterior pair frequently 

 elongated ; femora occasionally thickened ; claws unequal. 



Pictet : Eyes of the male each surmounted by a great 

 reticulated eye in the form of a turban that is to say, 

 borne on an abconical ring, at the base of which is the 

 ordinary eye ; wings, two or four, the superior (anterior) 

 having very few transverse nervures, which ordinarily form 



Female. Male. 



OUTLINE EYES OF CLOEON, MAGNIFIED (Pictet). 



two bent lines. The inferior (posterior) wings, when they 

 exist, are rudimentary, with nervation more or less in- 

 complete ; forceps of the male tolerably large ; two caudal 

 setas, with a slight trace of the middle or third. 



Eaton : Hind-wings absent, intercalar rudimentary vein- 

 lets of the terminal margin single in a large majority of the 

 species ; forceps four-jointed, basal joint short, relatively 

 stout ; intermediate abdominal segments of female sub-equal 

 in length ; caudal setae in male imago about twice, in 

 female one to one and a half, as long as the body. In the 

 sub-imago two-thirds and three-fourths as long. 



Eaton has placed a genus, Centroptilum, between Bae'tis 

 and Cloeon, having four wings, the hind-wing oblique, 

 elongate, and narrow, with the apex commonly obtuse, rarely 

 acute, and usually with the costal projection acuminate ; 

 neuration limited to two simple longitudinal nervures ; 

 fore-wings devoid of colour ornamentation, free from cross 



