320 Transactions. 



cj. Eyes approximated at a point anterior to ocellar triangle, the orbits 

 being strongly angulated ;• a naked area between the orbital angles and 

 ocellar triangle, so that, in profile, there appears to be an upper and a 

 lower tuft of hairs, the one on the ocellar triangle and the other on the 

 lower front ; 3rd antennal joint ferruginous ; face darker than in $ and 

 with darker reflections. Pleurae black with a greyish reflection, the hairs 

 ferruginous just beneath the orange-red spot under wings. Bristles of hind-legs 

 very distinct. Genital segments bristly, shown with the gentialia in fig. 62. 



S- Length, 13 mm. $. Length, 17 mm. 



Plesiotype : <J, No. 1240 ; $, No. 983, D. M. 



Habitat. — Throughout New Zealand ; uncommon in some parts, but very 

 common in others — e.g., Day's Bay, Wellington. 



Genus Helophilus Meigen (1822). 



The genus Helophilus may be characterized as follows : Eyes bare and 

 dichoptic in both sexes, though approximated in the male ; face concave 

 below antennae, but net dished, thence evenly convex ; oral margin from 

 the cheeks strongly descending (fig. 77) ; body not densely but rather 

 inconspicuously haired ; posterior femora thickened but not unusually so, 

 and sometimes with a tooth below near the base ; cell R t of wing open ; 

 vein Pi 4 + 5 distinctly curved into cell R 5 ; cross-vein r-m beyond middle 

 of cell 1st M 2 . Species usually large and robust, including the largest of 

 New Zealand Diptera ; metallic in colour or blue and black "with yellow 

 stripes and spots. 



Of the ten species already recorded from New Zealand, one has been 

 herein placed in the genus Mallota; another, described by the writer in 1910 

 as new, is now found to be a synonym of one of Walker's species. Further, 

 after a careful examination of Hutton's syntypes of vincinus, all of which 

 are females, it is apparent that this species is a variety intermediate between 

 the male and female of Schiner's antipodus. H. antipodus and H. trilineatus 

 resemble each other closely in both sexes, and since only the male of anti- 

 podus and the female of trilineatus have until now been described — the 

 former by Schiner and the latter by Fabricius — the males and females of 

 both species have been grouped by Hutton and others under antipodus and 

 trilineatus respectively. From the original descriptions by Schiner and 

 Fabricius the sexes and species can, however, readily be separated, the 

 main character being the presence in trilineatus (<# and $) of an inferior 

 tooth near the base of the posterior femora — " (femoribus) posticis 

 unidentatis " (Fabr.) — the presence or absence of which was not noted 

 bv later authors. 



Fig. 43. — Melanostomafasciatum: genitalia of male. 



Fig. 44. — Platycheirus lignudus n. sp. : antenna. 



Fig. 45. — P. lignudus n. sp. : anterior tibia and tarsus. 



Fig. 46. — P. lignudus n. sp. : diagram of abdomen of female. 



Fig. 47. — P. atkin-soni n. sp. : outline of head in profile. 



Fig. 48. — Xylota montana n. sp. : outline of head in profile. 



Fig. 49. — Platycheirus clarkei n. sp. : anterior tibia and tarsus. 



Fig. 50. — Tropidia bilineata : dorsal view of head of male. 



Fig. 51. — T. bilineata : dorsal view of head of female, showing colour-pattern. 



Fig. 52. — T. bilineata : outline of head in profile. 



Fig. 53. — Xylota montana n. sp. : genitalia of male. 



Fig. 54. — Tropidia bilineata : diagram of thoracic dorsum, showing colour-pattern. 



Fig. 55. — Xylota montana n. sp. : posterior femur. 



Fig. 56. — Tropidia bilineata : onychotarsus and appendages. 



Fig. 57. — Mallota cingulata : dorsal view of head of female, showing colour-pattern. 



