1. THEREVA 573 



conspicuous ; black bristles as usual ; pleurae with dense shaggy dull greyish 

 yellow pubescence, which may become darker yellow or even tawny and inore 

 conspicuous on the metapleurse. Scutellum with rather longer mixed 

 pubescence. 



Abdomen obscurely black or blackish brown on rather more than the basal 

 third of the second, third, and fourth segments, though the blackish colour does 

 not quite extend to the sides and is not sharply separated from the brownish 

 grey colour which covers all the rest (including all the sidemargins) except 

 the hindmargins of at least the second and third segments which are rather 

 broadly and conspicuously sharply margined dull yellowish, while the fourth 

 segment also has a similar but narrow hindmargin, and according to Loew 

 these narrow yellowish hindmargins may extend even to the_ seventh segment. 

 Pubescence in the best marked forms when viewed from behind all pale fawn- 

 colour and of almost equal densitj^ on all parts, but more commonly the 

 belly pubescence is dull yellowish white and slightly lighter than that on the 

 dorsal part because more or less numerous black hairs become inconspicu- 

 ously mingled with the pale hairs about the sidemargins and sides of the 

 hindmargin of the first segment, and also a few depressed black hairs occur 

 on the middle of the second and third segments near their hindmargins, while 

 still more such hairs occur on the fourth segment, and from thence to the 

 base of the genitalia longer more erect black hairs may become numerous on 

 the disc and even extend to the sides of the base of the genitalia ; in ordinary 

 specimens the pale pubescence is long and rather tufted about the sides of 

 the second and third segments, less abundant on the fourth segment, and 

 longer and more erect and less tufted on the next three segments, but rarely 

 (when viewed from above) the first segment may have numerous black hairs 

 intermixed near the sides of the hindmargin and predominating in the lateral 

 tufts, while the second segment may bear some such hairs, and the third 

 segment a few, while slightly tuft-like black hairs may occur on the sides of 

 the next three segments ; hardly any of these black hairs are noticeable when 

 viewed from behind, but the general pale pubescence seems to be a little 

 darkened. Belly blackish grey ; hindmargins of the second, third, and fourth 

 segments conspicuously, of the fifth segment narrowly, and of the sixth very 

 narrowly yellowish. Genitalia usually reddish orange on at least the large 

 lateral plates or about the base and lower part of the plates. 



Legs black ; tibiae luteous but blackened at just the tip ; tarsi with almost 

 all the basal joint and the base of the second joint and sometimes of even 

 subsequent joints brownish yellow. Pubescence on the anterior femora long 

 and pale greyish, (almost whitish), but on the front pair tending to beconie 

 more or less blackish about the tip beneath and behind ; hind femora with 

 recumbent scaly greyish yellow pubescence ; bristles as usual. 



Wings whitish hyaline with a slight brownish grey tint, but pale brownish 

 at the base and fore part ; stigma dark brown : veins conspicuously blackish 

 brown, very much intensified when viewed irom the wing-tip, and then 

 sharply contrasted with the whitish hyaline cells, but slight clouds occur 

 about the end of the submarginal cell and the upper part of the cubital fork- 

 cell, and the veins tend to reddish brown at the base and on the subcostal ; 

 slight blackish seaming may be found about the discal cross-vein and on the 

 discal vein in the dip between the discal and second posterior cells, while the 

 piece of the upper fork of the postical vein which forms part of the middle 

 basal cell is conspicuously blackish. Squamae smoky with brownish margins, 

 and with the fringes short and greyish white on the lower part but long as 

 usual about the fold. Halteres rather dark brown, stem paler. 



. Frons including the ocellar triangle greyish yellow to brownish orange ; 

 the shining black callus (fig. 323) divided into two fairly large spots which 

 though quite distinctly separated lie near each other and form a moderate 

 arch which is well remote from the lowest ocellus and all but or quite reaches 

 the eyemargins ; frons with short and rather spai'se black pubescence on tlie 

 front part which extends outwai'ds to the eyemargins but does not extend back- 

 wards, while a few shorter yellowish hairs occur in front close to the base of 

 the antennae and sometimes these pale hairs increase in number until they 

 extend almost from eye to eye (and Loew says until they even displace 



