221 



REVISION OF THE FAMILY EUSTHENIIDAE (ORDER PERLARIA) 

 WITH DESCRIPTIONS OF NEW GENERA AND SPECIES. 



By R. J. Tilly ARD, M.A., Sc.D. (Cantab.), D.Sc. (Sydney), F.L.S., F.E.S., 



Entomologist and Chief of the Biological Department, Cawthron Institute, 



Nelson, N.Z. ; formerly Linnean Macleay Fellow of the Society in 



Zoology. 



(Plates xi. — xv., and four Text-figures.) 



In a paper published recently in the Canadian Entomologist (Feb., 1921, 

 pp. 35 — 44), I have given a revision of thp classification of the Order Perlaria, 

 or Stone-flies, based on a study of the world fauna, with special reference to 

 the archaic gi'oups found in the Southern Hemisphere. In that reWsion, the 

 Eustheniidae are, for the first time, definitely recognised as a distinct family, and 

 tlieir characters clearly defined. These large and, for the most part, very beau- 

 tifully coloured Stone-flies are shown to possess only archaic family characters; 

 in other words, though existing to-day, they represent the original archet_ypic 

 family of the Order, from which all other types must have been derived. Their 

 principal characters, all of which will be readily recognised as archaic, are 

 the following: — ^the presence of five or six pairs of lateral abdominal gills in the 

 larva; the close correspondence between the wing-traeheation of the larva and 

 the wing-venation of the imago; the strongly formed imaginal mandibles; the 

 normal structure of the clypeus and lal)rum; in the imaginal wing-venation, the 

 aljsence of the transverse cord or anastomosis; the presence of cross-veins in all 

 parts of the wing, including the anal fan; the forewing with three anal veins; 

 the anal fan of the hindwing very large, and its margin forming a single con- 

 tinuous curve with that of the rest of the wing above the vena dividens (Cua). 

 This last character serves to distinguish the Eustheniidae at sight from all other 

 Perlaria. 



At the present time, only four species appear to have been descril)ed which 

 properly belong to this family. These are Eusthenia spectabilis Westwood 

 (1832) from Ta.smania, E. costalis Banks (1913) also from Tasmania. Sterui- 

 perla prasina (Newman), (1845), from New Zealand, and DJamphipuoa aii- 

 nulata (Br.). (18(i9). (=D. lichenalis Gerst, 1873) from Southern Chili. 

 EusthiSnia thalia Newm. (1839) from Tasmania, is not a true Eustheniid at all, 

 but belongs to the family Austroperlidae. In my previous paper, already cited, 

 I have proposed a new genus Tasmanoperla for the reception of this and the 

 closely allied species T. diversipes Till. 



