662 THEREVlD^ 



been closed ; sometimes the pale abdominal pubescence is brownish orange ; 

 the belly may be grey on the three basal segments, then shining and 

 blackish brown on the fourth segment, shining and still darker on the 

 fifth and sixth segments, until it becomes quite black on the seventh 

 segment. The female of T. bipundata is smaller, whiter, and always has 

 the frontal callus separated into two spots and the seventh abdominal 

 segment mainly pale haired ; T. plebeia has the shining black abdominal 

 bands more extensive than the whitish grey bands, the frontal callus much 

 larger, a clump of black hairs just below the eyes, and the last four 

 abdominal segments conspicuously black haired ; T. circumscripta has the 

 abdomen with black and almost white bands; T. arcuata has the black 

 abdominal bands more sharply defined, wider, and occupying more than 

 half the sidemargins, while the pubescence on the sides of the face and on 

 the fifth to seventh abdominal segments has fewer black hairs intermixed, 

 but (as in the male) I cannot well distinguish any brownish arc over the 

 end part of the discal cell ; T. fidva has the thorax and abdomen entirely 

 tawny haired, and has two pairs of prsescutellar bristles. 



T. nohilitata is distinctly the commonest and by far the most universally 

 distributed British species of the genus, but for all that is not what 

 can be called a common fly, though stragglers often occur in gardens 

 where I have found only this species and T. pleleia. While writing this 

 description (July 31, 1904) I have about 170 specimens of the species 

 before me and I have seen recently about 50 others ; a very large number 

 of these have been taken during the last few years by Colonel Yerbury, 

 more especially at Porthcawl and Barmouth in company with T. hi^nmctata 

 and T. annulata but not with T. pleleia, and it is mainly through these 

 specimens (which are nearly all in beautiful condition) that I have formed 

 my ideas of the limits of variation. Still, with all this material, I cannot 

 to my own satisfaction distinguish the males in some cases from some 

 males of T. pleheia ; I do not for a moment doubt their distinctness, as I 

 hardly ever have the slightest hesitation between the females of the two 

 species and all the tawny or orange haired males can at once be known as 

 T. nobilitafAi, but the difficulty lies in the more blackish haired males; in 

 these the browner ground colour of the thorax and brownish orange tinted 

 abdominal bands (when viewed from the sides) seem to distinguish 2\ 

 nohilitata from the blacker thorax and more ashy grey tinted abdominal 

 bands of T. pleheia. I have records of T. nohilitata from numerous 

 localities which extend from Penzance to Tongue, and consequently I 

 conclude that it may occur anywhere if sought for in June and July. On 

 June 20, 1907, the males were common on the leaves of nettles {Urtica 

 dioica) near Sudbourne in Suffolk, but only one female (and that in cop.) 

 was seen, but at the same time some rather large flies were executing a wild 

 frantic sort of dance in the air about ten feet from the ground in a 

 manner which reminded me of the dance of the males of T. annulata and 

 I have no doubt but that they were the males of T. nohilitata. My dates 

 extend from June 6 to August 29, which seem to prove it to be a rather later 

 species than T. -pleheia. A female specimen in such condition as to render 

 its identification doubtful was bred from a Lepidopterous larva in July, 

 1897, by Mr C. D. Ash, who also bred a male in June, 1901, from a 

 larva of Triplucna interjecta found in Essex, but this specimen is also of 

 rather doubtful identification as the soft pubescence is unusually grey for T. 



