98 DIPTERA OF NORTH A>rERICA. [PART IV. 



the British Museum, numerous specimens of Trochobola from 

 New Holland, Van Piemen's Land, and New Zealand, showing 

 that they are quite common there ; one of them, marked Limnohia 

 tessellata White, which I examined, showed precisely the same 

 distribution of the spots on the wings as T. imperialis or argus ; 

 I did not notice, however, whether the other specimens belonged 

 to the same species or not. 



In the Proc. Philad. Entomol. Soc. 186.5, p. 226, I had pro- 

 posed for this group the name of Discohola, which, being pre- 

 occupied, is replaced here by Trochobola (from rpoxoj, a wheel, 

 and j3axxw, I throw). 



1> T. argus Say. % and 9 . — Fuscano-flavida ; alis fusco ocellatis. 



Brownish-yellow, wings with ocellate brown spots (Tab. I, fig. 4). Long. 

 Corp. 0.25—0.3. 



Syn. Limnohia argus Say, Long's Exped. Append, p. 358. — Wiedemann, 

 Auss. Zw. I, p. 33, 17.— 0- Sacken, Proc. Ac. Nat. Sc. PhiL 

 1859, p. 217. 



Head, rostrum, palpi, and antenn® black ; thorax yellowish 

 with three brown stripes above ; the intermediate double ; pleurae 

 with two brown stripes ; halteres with a brown band across the 

 stem; knob likewise brown; abdomen brownish, genitals paler; 

 feet yellowish ; femora with a brown band at some distance from 

 the tip^ tip of the tibiifi and last joints of the tarsi infuscated. 

 Wings yellowish or whitish, with brown, ocellate spots especially 

 along the anterior and posterior margins ; the centre of these 

 spots, forming the pupil of the eye, is likewise infuscated ; these 

 centres are mostly placed at the origin or at the tip of the longi- 

 tudinal veins, or upon cross-veins : thus a complete ocellus has 

 the origin of the prtefurca for its centre ; a double one surrounds, 

 as centres, the inner end of the submarginal cell and the small 

 cross- vein ; other centres of less complete ocelli are the tip of 

 the seventh longitudinal vein and the supernumerary cross-vein, 

 existing there ; likewise the tip of the sixth vein and the inner end 

 of the fifth basal cell ; the apical portion of the wing contains 

 several more ocelli, more or less distinctly marked in different 

 specimens and giving that portion of the wing a variegated 

 appearance. 



Mah. Northwestern Territory (Say) ; Nova Scotia (British 



