21G EEV. A. E. EITON ON EECENT EPHEMERID^ OR MAYFLIES. 



boset with cilias intermingled sparsely with spines for some distance from the point 

 along its inner edge, and with a small tuft of hau* immediately below ; the spines are 

 not symmetrical in both maxillte of the first pair. Lacini* of maxillge ii. nearly of equal 

 breadth with the lobes of the labium, which nearly conform to quadrants of a circle ; 

 proximal joint of the palpus compressed and somewhat dilated inside before its extremity; 

 second joint slightly curved towards the base, enlarged distally and obliquely truncate, 

 equal in length to the third and half as long as the first joint ; third joint acutely sub- 

 ovate. Paraglossse rounded distally, narrower and shorter than the median lobe of the 

 tongue, which is widely retuse at the tip. Hind leg rather longer than the fore leg ; 

 tarsus (claw excluded) about as long as the tibia. Dorsum smooth ; pleurse of the inter- 

 mediate abdominal segments narrowly dilated oniscoidally, their outer edges nearly 

 straight for some distance from their points, and gently receding in a convex curve 

 anteriorly. Setge subequal in length ; the median plumose ; the outer ciliated inside and 

 approximately -^ as long as the body; in some species the fringes are conterminous 

 with the setDe, in others these are tail-pointed. 



Ti/2ye. S.Jlavidus (in XBaet'is), Ed. Pictet. 



Distribution. Eiirope, N. America, and Japan, in streams, rivers, and lakes ; species 

 more numerous in America, Northern Europe, and in mountainous regions than 

 elsewhere. 



Etymology . ai(p\oc, defective, and ovpa, tail, from the atrophied condition of the median 

 caudal seta. 



Subsequent to De Geer, no author appears to have noticed the nymph of Siphlurm 

 for upwards of a century. Dr. Hagen met with it in Prussia, but did not identify the 

 species or genus. The generical determination of the nymph was accomplished by 

 observation of *S'. lacustris in North Wales at the lakelet on Suowdon in the year 1868. 



EUROPEAN SPECIES. 



SlPHLUBTJS FLAVIDIJS, Ed. Pictct. 



XBaetis flavida, ! Ed. Pict., Synop. Nevropt. d'Esp, 24, pi. iii. 1-6 (1865). 



Siphlurus [type] fluvidus, ! Etn., Trans. Eut. Soc. Londou (1871), 125, pi. v. 30 [detail after Pict.]. 



Imago {dried). — ^. Notum and abdomen somewhat brown-ochreous, the latter with 

 longitudinal fuscous [brunes] markings on the hinder segments ; the venter is marked 

 with a series of strongly curved horseshoe-like or U-shaped lines pointing forwards. 

 Setae brown-ochraceous, with fuscous joinings. Wings vitreous, with a general faint 

 yellowish tint, and a Avell-pronounced yellowish stain at the base and in the pterosti^ 

 matic portion of the fore wing. Legs yellowish ochre, with fuscous joinings. 



5 . Very similar, but paler. Length of body 12 ; wing, s 12-5, $ 14' 5 mm. 



Sab. San Ildefonso, Segovia, Spain, in July (chiefly after Ed. Pictet). 



Siphlurus armatus, Etn. Plate XX. 34 e (forceps). 



Siphlurus armatus, ! Etu., Trans. Ent. Soc. London (1870) 6; \id., op. cit. (1871) 126, pi. vi. 1, la 

 [detail]. 



