new and Uttle-hiown Palsearctic Perlidw. 57 



dark reddish-brown ; legs reddish-brown, femora and tibiae tips and 

 the tarsi marked with fuscous. Forewings pale grey, sub-hyaline with 

 darker clouds, neuration fuscous ; hindwings clearer, slightly dark 

 at the tips. In the forewings the number of free nervures running 

 from the upper cubitus to the apical margin is usually two. The 

 darker cloudings are these : a vague blotch nearer the base, fol- 

 lowed by a broad median crescent and a narrow crescent, rarely 

 any evidence of an apical blotch. 



In the ($ the ventral plate is large, elongate, lateral margins 

 slightly inturned ; apex strongly recurved, its outline rounded and 

 entire. The genitalia are complicated and the nature of the 

 various parts uncertain ; two spiniform appendages are sometimes 

 visible in addition to those shown in fig. 1. Expanse of forewings : 

 cJ , 18-22 mm. ; ? , 21-28 mm. 



This insect has long been known to Dr. Eis from 

 Switzerland, and held by him to be a good species, con- 

 trary to the views of Albarda (expressed in 1889), who 

 considered it to be a form of T. trifasciata. It is, how- 

 ever, abundantly distinct from trifasciata in which the 

 ventral plate of the c? is shorter, the apex excised and 

 less recurved. In the present species also the antennae 

 are more slender, composed of longer joints, and having 

 no moniliform joints like those of trifasciata. The 

 smaller number of free nervures arising from the apical 

 portion of the upper branch of the cubitus (Albarda's 

 nomenclature = upper branch of inferior cubitus of 

 Nemoura, Trans. Ent. Soc. London, 1894, p. 574) is 

 also a useful character, although perhaps not absolutely 

 constant. It is also noteworthy that in trifasciata 

 there is usually a dark marking concave inwardly at the 

 very apex of the wing, of which marking there is rarely, 

 if ever, any trace in T. Risi. 



As indicated, T. Bisi has been found in Switzerland 

 (Zlirichberg) by Dr. Ris, and amongst Mr. McLachlan's 

 continental material there are ? 's which I refer in the 

 meantime to this species from the following localities : 

 Albania (S. S. Saunders) ; Pyrenees (Eaton, 10th June) ; 

 France (Ardeche, May, Fallou ; Vosges, 20th July, 

 McLachlan) . 



In Britain it is probably generally distributed wher- 

 ever there are fairly rapid streams. Mr. McLachlan has 

 it from Haslemere, Surrey (July) ; Rannoch (between 2nd 



