NISONIADES. 261 



in Pyrgus and Scelothrix ; the apical joint thick, bluntly conical, somewhat bent. 

 Tibiae unarmed, with long hairs. Forewings triangular, outer margin not toothed ; 

 fringe unicolored. <? with longer costal fold. — Nisoniades — montanus, Brem. ; 

 tages, Linn. 



Club of antennas elongated, curved, shorter than in Nisoniades, suddenly 

 swollen, and scarcely contracted at the well-rounded tip. Forewings more elongated 

 than triangular, the front margin more steeply arched above the base, the hind 

 margin shorter. <5 destitute of the costal fold. All the other characters, as in 

 Nisoniades. — Hallia [Thanaos] — marloyi, Bdv. 



Thanaos, as has been already shown, is a synonym of Nisoniades, 

 having the same type, tages. We have, therefore, suggested Hallia 

 to take its place, and would name marloyi, Bdv., the type. 



Speyer (op. tit., p. 169), writing of Nisoniades, notes that " the 

 peculiarly native country of this genus, scarcely represented in Europe, 

 is North America. The characteristic feature is the form of the club 

 of the antennae, which is fusiform when stretched out, but which takes 

 the form of a narrow crescent when in its regularly curved condition. 

 This fundamental form is constant ; the stoutness of the club and its 

 degree of acuteness differ according to the species. In some American 

 species it is very slender and finely pointed ; in others, as in N. tayes, it 

 is thicker and more blunt, but never so suddenly rounded as in 

 Scelothrix or Thanaos (Hallia, supra). The species montanus, Brem., 

 is distinguished by the particularly large hindwings, with expanded 

 margin, also by the difference of colour and marking ; the antennal 

 club is somewhat thicker than in N. tages, but is otherwise of the same 

 shape." 



With regard to the costal fold, by means of which Nisoniades (as here 

 restricted) is to be specially distinguished from Hallia, Aurivillius gives 

 (Bid. Sv. Vet. Akad. Handl.,y., p. 83) the following detailed account (with 

 figures) thereof. He writes : "As in the preceding genus (Hesperia), the 

 male here is also furnished with a so-called costal fold. This costal fold 

 of the Hesperiids has long been known, and also been made use of as a 

 sexual character by many authors. The structure, as far as I know, 

 has never been exactly described. With the aid of the figures 24 and 

 25, the first of which depicts the fold in section, and the latter the 

 same unfolded and viewed from the upperside, I will endeavour to give 

 a more exact description of the structure. When it is quite closely 

 folded over, it appears merely as a thickening of the costa, and the 

 scales are set into each other so closely that it is difficult to discover the 

 opening. If one makes a section of it in this condition, one finds the 

 roof of the tube thus formed consists mostly of large and long- 

 scales (a) attached to the edge of the costa ; these meet other similar 

 scales (/), which stand almost upright from the wing membrane, 

 along the lower margin of the tube. The costal margin (b) is very 

 narrow and insignificant ; then a tube (</),■ immediately following this, 

 runs along the wing, which tube does not, like the usual wing- 

 nervures, form a swelling or elevation on the underside, but on the 

 upperside, of the wing. This tube occurs in both sexes, and also in 

 those species in which the costal fold is absent, though, in these latter 

 it is less developed. It appears to me as though one could look on it 

 as a true costal nervure, which one so far has denied to the butterflies, 

 which may easily be explained, for this rib, looked at from that point 

 of view, appears only as a dark band running along the costal margin. 

 That it is really a tube may be also perceived from the fact that it 



