THE INSECTS. 343 



In the genus Ccem's, Stephens says : " This genus is 

 readily known by the brevity of its wings and abdomen, 

 the latter not exceeding the length 

 of the thorax ; its apex furnished with 

 three setce, by which character alone 

 it may be distinguished from the 

 two following genera Baetis and 

 Cloeon" 



According to Pictet, the head is 

 short and large ; eyes simple in both 

 sexes, and always separated by a 

 considerable space ; wings, two, with 

 very few transverse nervures ; body WI <- 

 short and thick; three setae; very 2. CLOEON, WITH FORE 



. .' , , L . ^, WINGS ROUNDED AT APEX. 



long in the male, very short in the 



female. These in sects are very local, but occur occasion- 

 ally in great swarms. 



The genus Heptagenia (Eaton). The Heptagenia sul- 

 plmrea is the Baetis elegans of Stephens and Curtis, and 

 Baetis cyanops of Pictet, one of the Yellow Duns. Hep- 

 tagenia flavipennis. Baetis longicauda (Stephens), Cercea 

 (Pictet), another light Yellow Dun, the " yellow uprights " 

 of Devonshire. 



The exact identification of the names by which artificial 

 flies are known to anglers with the natural insects, parti- 

 cularly in the smaller genera and species of the Epheme- 

 ridce, is no easy task. 



The state and age of the insect, the time of year, the 

 different atmospheric conditions, produce various shades 

 of colour both in wings and body. At one time an olive 

 tint, at another a yellow, or grey, or brownish-red. 



The different nomenclature of the northern and southern 

 counties is also another difficulty. In the north most of 

 our southern duns are classed as drakes, the duns being 

 taken chiefly from the Phryganidce ; whilst in the south the 

 duns are almost all from the Ephemeridce. 



With few exceptions, we must, until each species has 

 been more clearly defined and verified by microscopical 

 investigations, rest satisfied to place the various duns, 



