61 [August, 



by the external transverse vein of the wings being less oblique ; and by the internal 

 transverse vein being placed very slightly behind the centre of the discoidal cell, 

 which may be considered as the most characteristic point of distinction. I am not 

 acquainted with the female of this species, and it is not described by Zetterstedt. 

 The specimens which I have named duplaris differ in some respects from the de- 

 scription given of that species by Zetterstedt, so I am not certain that they are 

 identical with those he described. Eondani, to whom I sent this fly, together with 

 the last, said that he considered I had rightly named it duplaris, Zett. ("talem esse 

 cogito "). This species is not common. The only specimens which I have seen were 

 captured in the neighbourhood of Edinburgh. 



S. communis, Desv. 



In general colour, form, and design, this species closely resembles 8. duplicata, 

 but it is generally rather larger, and always has the tibiae more or less tinged with 

 red or yellow. The females usually have the legs much paler than those of the other 

 sex, but the middle and posterior tibia? are sometimes quite testaceous, even in the 

 males, though in the most common variety the legs are so nearly black, that the red 

 tinge, which is then confined to the posterior tibia?, may easily be overlooked, and 

 this species may then be confounded with S. duplicata. 



Macquart only knew the male, which he named S. ccesia. His description is 

 good though short, and applicable to the black-legged variety ; for he says, " Pieds 

 noirs ; jambes quelquefois d'un testace noiratre." R. Desvoidy described this species 

 (especially characterizing the female) under the name of (Mi/dina) communis, which 

 name I have adopted, as it has the priority over that of ccesia, and is also very ap- 

 propriate, from the general diffusion and abundance of this fly. Apart from the 

 different colour of its legs, S. communis differs from S. duplicata, in the males, by 

 having the lines on the thorax usually more distinct ; the external transverse veins 

 of wings more oblique, and often more clouded, as well as sometimes sinuous ; by 

 the internal transverse vein being placed further back, being about one-third from 

 the end of the discoidal cell, instead of two-fifths ; by the antenna? having the third 

 joint rather longer in proportion ; and by the calyptra being yellower and having 

 the lower scale rather smaller than in 8. duplicata. The females of S. communis 

 cannot easily be confused with those of 8. duplicata. They differ from the males of 

 their own species, by having the thorax often indistinctly marked with the lines 

 brown instead of black, and the spots on the abdomen small and also brown. The 

 external transverse veins are also often much less oblique (this character varies much 

 in both sexes), and the legs have the tibia? and knees, as well as the ends of the 

 femora, of the middle and posterior pairs, mostly distinctly testaceous, with a rufous 

 tinge on the bases of the anterior tibia?. 



S. QUADRUM, Fab. 

 This is a very difficult species to define. It closely resembles some of the pale- 

 legged varieties of S. communis, and I know of no decided characters by which the 

 females of the two species can be separated. The males differ by the eyes bring 

 rather more widely separated in 8. quadrum than in 8. communis ; by the thorax 

 being less distinctly striped (sometimes almost unstriped) in the former than in the 

 latter; by the wings in 8. quadrum being tinged with yellow at their bases; being 



