1. THEREVA 555 



segments ; seventh and eighth segments with numerous short black stubby 

 bristles. Belly greyish black on the three basal segments, more blackish 

 but still dusted on the next three, and rather shining black on the seventh, 

 while the bare brightly polished apparent eighth segment forms the under- 

 side of the base of the ovipositor ; hindmarginal hems conspicuously pale 

 yellow and unusually broad on the second and third segments, narrow on the 

 fourth, and only just visible on the fifth ; pubescence on the second and 

 third segments long, thin, sparse, erect, and yellow, on the fourth segment 

 shorter but still pale, on the fifth segment more rigid and mainly black, and 

 on the sixth and seventh segments all black. Ovipositor almost all black, 

 but some of the spines on the apical circlet have a slight lurid red tinge 

 and some longer bristles immediately against the hindmargin of the seventh 

 ventral segment are conspicuously lurid red. 



Legs similar to those of the male, the tibiae (especially the anterior) and 

 tarsi being darker and more extensively black than in T. nobilitata so that 

 the tarsi are ferruginous at only the extreme base of the posterior pairs ; 

 anterior femora with longer postero-ventral pubescence than in T. nobilitata ; 

 antero-ventral bristles on the femora about three on the front pair, three 

 on the middle, and seven on the hind. 



Wings similar to those of T. nobilitata, and without any cloudings unless 

 a faint arc can be traced above the end portion of the discal cell. Squamae 

 with darker margins. 



Length about 11 mm. 



This species, as I understand it, does not seem to vary much in its 

 handsome form. The tufts of black pubescence in the male on the dorsal 

 line of the abdomen may resolve themselves into black triangles on the 

 second, third, and fourth segments, and the greyish orange bands may 

 not reach the sidemargins, so that these may appear all black except 

 on the bright orange hindmarginal hems, or the bands on the fifth to 

 the eighth segment may be more greyish and a little less orange, while 

 the seventh and eighth segments may be entirely but inconspicuously 

 brownish ashy grey ; the golden pubescence may be more extensive but 

 by no means dense ; the prsescutellar bristles on the thorax have a strong 

 tendency in both sexes to form two pairs as in T. ftdva, but this is more 

 common in the female, and again in the female it is more common to find 

 the fourth posterior cell even wide open in both wings, though when it is 

 narrowly open in one wing it is often closed in the other, but the male 

 shows this tendency in a minor degree. It may be rather difficult to 

 distinguish it from tawny haired specimens of T. nobilitata, but in the 

 male the conspicuous velvety black entire abdominal bands form an obvious 

 distinction, while the general rufous orange coloration is conspicuous in 

 comparison with the greyish fulvous pubescence of T. nobilitata; numerous 

 small distinctions may be found in the fewer black hairs on the middle 

 part of the face, more numerous black hairs below the lowest angle of 

 the eyes, more conspicuous thoracic lines, frequent occurrence of two pairs 

 of prsescutellar bristles, yellower scutellum, black tufts of pubescence at 

 the sides of the abdomen near its tip, and longer pubescence and bristles, 

 blacker tibise and tarsi, etc., but I cannot trace any good distinction in the 

 cloudings on the wings. The female has a slightly larger and differently 

 shaped frontal callus which extends more to the eyemargins (though the 

 shape of this occasionally varies in all species of the genus), and in cases 

 of doubt may be distinguished by the blacker tarsi. 



T. arcuata (as described above) is apparently a species limited with 

 us to North Scotland as I have seen it from only Nethy Bridge, Golspie, 

 Brodie, Logic, and Forres, from July 27 to September 9. I have never 



