308 Transactions. 



outline shown in fig. 38 ; cheeks black with a greyish reflection ; proboscis 

 and palpi black, the latter sometimes brownish ; occiput black with grevish 

 reflections. 



Thorax brilliant bronze, with a tawny pubescence on dorsum ; scutellum 

 brilliant blue-black. Legs tawny, sometimes fuscous, with tawny knees. 

 Wings clear, iridescent ; veins and stigma brown ; halteres pale yellow. 



Abdomen elongate, rectangular, the sides almost parallel ; shiny blackish- 

 brown, but mostly occupied by the tawny or orange-red spots on the 2nd, 

 3rd, and 4th segments (fig. 39) ; the spots on the 2nd segment are the 

 smallest, those on the 3rd and 4th occupy the whole of each segment 

 except for a narrow median stripe and a band across the posterior margin 

 which widens at the sides. The genitalia are tawny, the structure of the 

 genital segments being shown in fig. 43. 



$. Eyes dichoptic ; front and vertex shiny black and clothed with 

 short black hairs ; a narrow silvery reflection along frontal orbits ; a narrow 

 transverse brownish band constricted in the middle and followed by a suture 

 to be seen in some lights across the middle of front. Antennae altogether 

 tawny except for a blackish apical area. 



Thorax shiny bronzy -black ; scutellum shiny black ; the whole clothed 

 with a tawny pubescence. Legs ochreous, the posterior tibiae distally 

 and the tarsi fuscous. 



Abdomen (fig. 40) ovate, shiny blue-black with a pair of ochreous spots 

 on the 2nd, 3rd, 4th, and 5th segments, the last pair transverse, the 

 remainder rather dome-shaped, those of the 2nd and 3rd segments narrowing 

 to the sides ; apex of retracted segments tawny. 



The intensity of the abdominal spots varies according to location and 

 age : in the milder parts of the country they are more tawny, but in 

 warmer localities they are of a rich orange-red. 



The female deposits her yellowish eggs (Plate XL VIII, fig. 6) in pairs or 

 sometimes singly upon plants infested with aphides and lepidopterous larvae. 

 The larvae of M. fasciatum are yellowish and semitransparent with a 

 darker medio-longitudinal stripe ; at the anterior end is a smooth shiny area. 

 Plate XLIX, fig. 1, shows one of the larvae at rest on the underside of 

 a rape-leaf. Large numbers of aphides and the larvae of the diamond-back 

 moth (Phitella maculipenis) are destroyed by this syrphid. The pupae are 

 short, club-shaped, and brownish, and may be found attached to the 

 underside of leaves frequented by larvae. 



<J and $. Length, 6 mm. 



Plesiotype : No. 1238, D. M. 



Habitat. — Throughout New Zealand, from spring to autumn. 



M. apertum Hutton. 

 M. apertum Hutton, Trans. N.Z. Inst., vol. 33, p. 42 (1901). 



Hutton's type, the only specimen as yet known, has lost the 2nd and 

 3rd joints of one antenna and the 3rd of the other. Owing to the length 

 of the existing 2nd joint, it is doubtful if this species belongs to Melano- 

 stoma ; however, it is retained here for the present until complete specimens 

 are procured. 



A small shiny blue-and-black fly with tawny legs and no colour- 

 pattern. 



$. Eyes bare, dichoptic ; front and face shiny bronzy-black with a 

 greyish tomentum ; ocelli yellowish, the ocellar triangle with delicate erect 



