42 Transactions. — Zoology. 



continuous in the male. The segments are also narrowly 

 margined with tawny. Legs tawny ; the bases of the fore 

 and middle femora and the whole of the hind femora black. 

 In the male the hind tibiae have a dusky band. Length, 

 3 8mm., J 9 mm.; wing, $ and $ 7 mm. 

 Hob. Auckland (Captain Broun). 



Genus Melanostoma, Schiner (1860). 



Medium size, nearly bare, metallic-black or greenish-black, 

 the abdomen with lighter-coloured spots or bands. Antennas 

 short, third joint oval or a little elongate. Face tuberculate, 

 black or black-green, never in ground-colour yellow, though 

 frequently with whitish dust. Eyes bare, contiguous in the 

 male. Thorax shining, without yellow or red marks. Abdomen 

 elongate, slender, rarely oval, much flattened. Legs simple, 

 the hind metatarsi sometimes a little thickened. Wings rather 

 large, extending beyond the abdomen ; marginal cell open ; 

 third longitudinal nearly straight ; outer anterior angle of first 

 posterior cell acute. 



Plesia, of which M. fasciatum is the type, has priority of 

 Melanostoma. 



Key to the Species. 



Abdomen with testaceous spots .. .'. .. M. fasciatum. 

 Abdomen black. 



Scutellum seneous .. .. .. .. M. avertum. 



Scuttllum black.. .. .. .. .. M. decessum. 



Melanostoma fasciatum. 



Plesia fasciata, Macquart, Dipt. Exot., Supp. 4, p. 461, 

 tab. 14, fig. 15 (1850); Hutton, Cat. Dipt. N.Z., p. 45. 



Face and vertex black. Antennae black, the third joint 

 oval. Thorax and scutellum aeneous. Abdomen oblong in 

 the female, linear in the male ; black ; the second, third, and 

 fourth segments with a large testaceous spot on each side, 

 larger in the male than in the female ; the fifth segment tes- 

 taceous anteriorly. Legs tawny, the hind pair more or less 

 fuscous. Length, 6 mm. ; wing, 5 mm. 



Hab. Christchurch, Whangarei, and Queenstown (F. W. H.). 



The second longitudinal vein is nearly straight, very 

 slightly curved forwards at the tip. 



Melanostoma apertum, sp. nov. 



Female. — Vertex and face black. Thorax and scutellum 

 aeneous. Abdomen oblong, bluish-black, without any bands. 

 Legs tawny. Wings colourless, the stigma pale-yellow ; 



