238 PROF. M. BEZZI. 



on the line of the a. sa. ; the small cross-vein is beyond not before the middle of the 

 discoidal cell. The upper terminal angle of the third antennal joint is acute but not 

 produced. 



2. Trirhithrum nitidum, v. Roder, Berl. Ent. Zeits., xxix, 1885, p. 134. 



Described from Delagoa Bay, and very distinct from the other species on account 

 of the complete middle band of the wings. Not found subsequently. 



3. Trirhithrum albonigrum, Enderlein, Zool. Zahrb., xxxi, 1911, p. 410, fig. A. 



Described from Camerun, Barombi, and nearly allied to the preceding species, 

 from which it is distinguished by the interrupted middle band of the wings. 



4. Trirhithrum nigrum, Graham, Bull. Ent. Res., i, 1910, p. 162, pi. xii, fig. 1 



(obscurum, Enderlein, 1911). 



The present species seems to be widely spread in West Africa, being recorded from 

 South Nigeria, Camerun and the Belgian Congo. I have never seen it, but only the- 

 following form, which seems to be distinct, at least as a variety. 



5. Trirhithrum gagatinum, sp. nov. 



Nearly allied to the preceding species, and perhaps Only a variety of it, differing 

 in its black face and the entirely infuscated costal cell of the wing. 



$. Length of body, 5*5 mm. ; of ovipositor, 1*5 mm. ; of wing, 5 mm. 



Occiput entirely shining black, only dark reddish below at sides ; frons dark 

 yellow, purplish above the antennae, with a black ocellar spot ; face shining black, 

 with the upper mouth-border narrowly reddish ; jowls dark reddish, with a brown 

 spot below the eye. Antennae blackish brown, with a broadly plumose arista. 

 Palpi grey, very broad, with short, black, bristly hairs ; proboscis reddish brown. 

 All the bristles are black, like those of the thorax and scutellum ; 2 i. or. ; oc. very 

 strong ; dc. a little behind the line of a. sa. ; 1 mpl. ; pt. strong. Thorax entirelv 

 shining black, even on the pleurae, with the humeri very narrowly and in distinctly 

 reddish ; pubescence of back short and entirely black ; hairs of pleurae longer, but 

 likewise black. Scutellum entirely shining black, only at the sides in distinctly 

 reddish, without yellow apical dots below ; ic bears four bristles, and black, rather 

 stout hairs. Mesophragma shining dark brown, like the hypopleura. Halteres black, 

 with brownish stalk. Abdomen entirely shining black, dark brownish at base, with 

 black hairs and numerous black bristles on sides at end ; the transverse band of 

 whitish dust on third segment is narrow and abbreviated at the sides ; the 

 pubescence above it is whitish. Ovipositor triangular, shining black and black 

 pilose ; apical segment reddish. Venter shining black, with brown base. Legs 

 with coxae and femora black, tibiae and tarsi pale yellowish, but the four posterior 

 tibiae are broadly blackened at base ; bristles, spurs and hairs black ; hind tibiae 

 with 4-5 short black bristles at the middle of the posterior edge. Wings as in 

 nigrum, but with the base entirely infuscated along the costal cells and with the costal 

 vein entirely black ; the cubital band seems to be broader, covering the whole of the 



