Milleb and Watt. — Study of New Zealand Entomology . 281 



Wings (fig. 13) moderately broad, colourless except for pale yellow at 

 the articulation ; when closed, extending considerably beyond the abdomen ; 

 costa (c) ending some distance from tip of wing ; auxiliary vein (aux) indis- 

 tinct, well separated from the 1st longitudinal vein, but evanescent distally ; 



13 



FlG. 13. — Wing- venation. P. albiceps. 1. 1st longitudinal; 

 2, 2nd vein; 3, 3rd vein; c, costa; aux, auxiliary 

 vein ; acv, anterior cross-vein. 



1st longitudinal (1) sinuated upward toward the costa; 2nd vein (2) only 

 slightly sinuated ; 3rd vein (3) uniting with the distal extremity of the costa ; 

 anterior cross-vein (acv) situated well before the middle of the wing and the 

 end of the 1st longitudinal vein : posterior veins and basal cells indistinct. 

 Halteres pale yellow. 



Legs bristly, black with pale-yellow knees ; femora comparatively thick- 

 ened : tibiae shorter than the femora : tarsi considerably longer than either 

 the femora or tibiae, the metatarsi being about one-third the length of the 

 whole tarsal joint ; 2nd tarsal joint about one-half the length of the meta- 

 tarsus : claws small, pale yellow on proximal half, but black distally, the 

 inner proximal angle of each protruding knob-like ; pulvilli pale yellow, 

 with a vestiture of delicate hairs : empodium a strong bristle ; a small 

 apical bristle on inner angle of middle tibiae : anterior femora with longer 

 bristles on the lower side. 



Abdomen about as long as the thorax, but not as broad, narrowing toward 

 a rounded apex ; black in ground-colour, but with a minute greyish pubes- 

 cence. When ventrally examined the genital cavity is heart-shaped, the 

 margin being beset with short bristles, from among which protrude the pale- 

 yellow copulatory organs. 



The female fly appears to deposit her ova on both surfaces of the leaves 

 of the food plant. Close observations show that the upper side is almost 

 invariably preferred, the majority of eggs being laid on the outer margin 

 of the leaf. Having selected a suitable spot for oviposition. the fly lowers 

 her ovipositor till it is at right angles to the surface of the leaf, having to 

 stand on tip-toe for the purpose : with several downward jerks of the abdo- 

 men the ovipositor is thrust through the cuticle and pushed beneath its 

 surface, pushing at first directly backwards and later laterally, in this way 

 prizing up the cuticle so as to form a minute semicircular pocket in the 

 leaf (Plate III, fig. 1). After a moment's rest the ovipositor is withdrawn, 

 leaving a single egg within the pocket. Some- little time after the cavity 

 has been made the separated cuticle dries, and the whole becomes visible 

 to the naked eye as a minute white .spot on the leaf. 



While engaged in laying, the fly is very sluggish, and can be closely 

 observed with a magnifying-glass without taking to flight, and can even 



