332 THE RIVER-SIDE NATURALIST. 



its last integument and assuming the imago or perfect 

 state. 



Pictet. EPHEMERA DANICA. Male Imago (perfect insect). 

 Head black ; thorax black, brown 

 above ; mouth yellow ; all the rest 

 of the body of a pale-yellow chest- 

 nut-brown ; abdomen marked with 

 four rays above and under the lateral 

 marks on the upper segments and 

 six on the lower ; wings transparent, 

 colourless with brown nervures, the 

 subcostal thicker and darker than 

 the others ; anterior legs brown, with 

 tawny tarsi, other legs tawny ; setae 

 pale-brown, tinged with black. Spots 

 on the wing form an incomplete 

 band as in E. vulgata, a large spot 

 EPHEMERA DANICA (Pictet). near the base of each anterior wing. 

 E. LINEATA (Eaton). Posterior wing with no centre spot, 



but bordered with brown. 



Female Imago. Colouring generally lighter than the 

 male ; spots on the wing less distinct. 



Sub-Imago. Darker in colour ; has a light spot shaped 

 like a lance in the middle of the meso thorax. 



Eaton. EPHEMERA DANICA. Male Imago. Head and 

 thorax, upper part deep blue-black, polished ; face, mouth, 

 pale greenish-yellow ; abdomen, the first four or five dorsal 

 segments ivory-white, with a pale anereous broad triangular 

 blotch at the base on each side, the hinder segments varied 

 with pitch -brown, or deep-brown ochre; wings faintly 

 grey-tinted, most distinctly so towards the anterior terminal 

 margin and in contiguity with the black nervation ; spots 

 on the wing pitch-brown, but not so distinctly marked 

 as in vulgata; legs pitch-black, hinder pair tinged oliva- 

 ceous ; the fore-wings darkened ; setae black ; forceps sepia- 

 brown. 



Sub-Imago. Wings at first greenish-grey, becoming 

 greyer, variously edged with grey-black along the terminal 

 margin ; discal spots and most of the cross veinlets black ; 



