240 PROF. M. BEZZI. 



The present species is evidently allied to the following ones, chiefly to the 



var. hucopsis ; but it seems to be distinguished by the broadly hyaline base of 



the wings and by the pale-coloured halteres. 



» 



8. Trirhithrum nigerrimum, Bezzi, Boll. Lab. Zool. Portici, vii, 1913, 



pp. 25 & 36, fig. 3 ; Silvestri, I.e., viii, 1913, p. 67, fig. xiii. 



Bred from various fruits, but especially from coffee berries, by Prof. Silvestri 



in S. Nigeria, Lagos and Olokemeji ; Gold Coast, Aburi ; and Camerun, Victoria. 



Described originally by me as a variety of nigrum, and subsequently recognised as a 



different species by Prof. Silvestri. None of the specimens that I have seen were in 



good condition, and thus it is not possible at present to have a sure knowledge of this 



species, which seems to be variable ; this variability may perhaps be connected with 



the fact that the specimens were bred from different plants ; some related forms 



may be present. The colour of the face seems to vary from entirely white to 



entirely brown ; the wings sometimes have a small hyaline indentation at the base 



(see my figure, in which the basal band is represented too broad at its lower end), 



which is usually not present. 



9. Trirhithrum nigerrimum, var. leucopsis, var. nov. 



Distinguished by the cream-white face and the hyaline indentation of the 

 costal cell. 



(J o Length of body, 3*5-4 mm. ; of wing, 3*5-4 mm. 



Occiput entirely black, only below at sides narrowly pale yellowish ; frons in 

 both sexes yellowish grey, with two more or less distinct dark transverse bands 

 towards the middle and with a black ocellar spot ; face quite white, like the narrow 

 jowls, which bear a dark spot below the eyes ; the face is more or less distinctly 

 infuscated above, near the root of antennae. Antennae entirely yellowish, with a 

 broadly plumose arista ; proboscis black ; palpi greyish brown. Cephalic bristles 

 black. Thorax entirely black, even on the humeri, pleurae, hypopleurae and 

 mesophragma ; the short pubescence of the back is whitish, while the longer hairs 

 of the pleurae are black ; chaetotaxy normal, with black bristles. Scutellum like 

 the thorax, but with two very small yellowish dots on middle of hind border, below 

 the set. Abdomen shining black, its grey markings as in occipitah, but those of the 

 third segment not triangular in shape ; ovipositor shining black, 0'7 mm. long. Legs 

 black ; tibiae and tarsi pale yellowish, but the tibiae more or less broadly blackened 

 at base ; hind tibiae with a complete row of bristles. Wing pattern and shape 

 of discoidal cell as in occipitah. 



Type (J (British Museum), a single specimen from Nyasaland, Limbe, 4,000 ft., 

 22nd September 1916 (R. C. Wood). 



This specimen was caught together with the $ type of occipitah, but I think it is 

 unlikely that it is the other sex of that species, owing to the different coloration of 

 the head and chiefly of the pubescence of the back of the thorax, which in the 

 known species is always similarly coloured in the two sexes. Besides, I have received 

 from Dr. Mochi a couple of specimens from Erythraea, Ghinda, December 1916, 

 in which the female has the head coloured as in the male, and has whitish pubescence 

 on the back. 



