580 THEREVID^ 



blackish ; anterior femora with, the front side of the notch beneath the tip 

 (into which the base of the tibiae folds) rather produced downwards. 

 Pubescence on the coxse, abundant, long, and white, with two or three 

 black bristly hairs near the tip, and on the hind cox» with one rather 

 conspicuous strong black bristly hair outside near the tip ; trochanters 

 almost bare ; anterior femora with long shaggy white pubescence 

 beneath and behind, but the hind femora with hardly any similar 

 pubescence except near the base in front. Bristles (black) consisting of 

 two or three antero-ventral on the anterior femora near or rather before 

 the middle, and a row of about eight on the hind femora which do not 

 quite extend to the base ; front tibiae with three dorsal bristles and about 

 five postero-ventral (but two of these very small) ; middle tibiae with similar 

 bristles, but the dorsal ones stronger, and with three minute postero-dorsal, 

 the antero-ventral bristles being after the middle and also strong ; hind 

 tibiae with four rows of bristles (dorsal four, postero-dorsal four, antero- 

 ventral four, and postero-ventral four to six very small) ; apical circlets of 

 spurs on the posterior tibiae rather strong, but the circlet on the front pair 

 much weaker (except one bristle) ; basal joint of the hind tarsi rather thickly 

 beset beneath with plantar bristles ; front tarsi with some small " touch- 

 hairs " beneath the basal joint. Claws and pulvilli small, brown. 



Wings (fig. 325) with a whitish glossy shimmer, and with the costal, end 

 of subcostal, and the basal veins orange, but the other veins blackish and 

 sharply defined ; stigma yellow ; fourth posterior cell almost always closed, 



Fig. 325.—Thereva annulata $ . x 10. 



or at any rate _ very much narrowed to the wingmargin. Squamae (alar) 

 rather large, whitish with a conspicuously black base, and with a short white 

 fringe on the upper part but a long pure white fringe on the lower part ; 

 frenum forming only a whitish grey line. Halteres yellow, but the broadened 

 end of the stem blackish. 



Frons at the vertex less than one-fifth the width of the head, but quickly 

 widening so that at the antennae it is about half the width of the head, and 

 the eyes continuing to diverge down to their lowest margin ; frons rather 

 light brown on the upper two-thirds and bearing there short black bristly 

 pubescence which is directed forwards, but the rest of the frons and all the 

 jowls and back of the head white and bearing long white pubescence similar 

 to (but not so long nor so pure white) as in the male ; this pubescence 

 does not commence quite close to the black pubescence on the frons, and on 

 the back of the head is rather greyish white ; back of the head much more 

 inflated than in the male because the eyes are smaller, and on the upper 

 part on each side with a postocular row of about nine strong black bristles 

 which are rather bent forwards, while on the upper part of the extreme back 

 of the head are about twenty smaller black bristles. Antennae with 

 the pale pubescence on the basal joint shorter and less pure white. 



Thorax dull brownish black with the light grey lines not always obvious, 

 clothed and obscured with short greyish white decumbent pubescence, inter- 

 mixed with which are some inconspicuous erect darker hairs, but these 

 together and 'even with the addition of some grey dust are not quite abundant 

 enough to conceahthe ground colour • pubescence longer and more erect above 

 the wing-base, on the postalar calli, and across the hindmargin; pleurae 

 with very different pubescence composed of thinner more sparse almost silky 

 long hairs, which are numerous only on the prothorax and the metapleurae 

 and probably the mesopleuras (but easily abraded). The strong black bristles 



