20 Syrphidae. 



cases it is long-plumose with long rays above and below. The antennæ 

 are not rarely larger in the female than in the male, very rarely on 

 the contrary largest in the male (Liogaster). Epistoma as a rule 

 rather broad, rarely narrower; it varies otherwise considerably in 

 shape; generally it is more or less hollowed below the antennal pro- 

 minence, then raised to a smaller or larger central knob, below which 

 it is again hollowed with a prominent upper mouth edge; often it is, 

 however, only retreating below the central knob, not being raised 

 again at the mouth edge; the whole lower part of the epistoma with 

 the central knob may be more or less protruding; in other cases the 

 epistoma goes straight or almost so from the antennæ to the mouth 

 edge, only being a little arched or sometimes keel-shaped ; in a few 

 cases the central knob and the upper mouth edge are fused together 

 and prominent, sometimes very much prominent forming a protruding 

 bec, The epistoma may be more or less descending, from not, or al- 

 most not, to rather strongly, and in. the latter case it is generally 

 pointed below. The oral aperture is generally elongated, only when 

 the epistoma is straight, not at all protruding below, the aperture is 

 more or less roundish ; on the other hånd it is long and narrow when 

 epistoma is strongly protruding; it has otherwise generally a special 

 shape on account of the shape of the oral margin; this margin goes, 

 forming the side mouth edges, from behind straight forwards, or when 

 epistoma is descending, downwards; the side mouth edges end in 

 front on each side with a more or less angular and often more or 

 less drooping point, the lateral angles; between these the anterior 

 margin, the front mouth edge, forms a curve which goes forwards 

 and generally more or less upwards; this characteristic shape may 

 be more or less pronounced, depending especially on the more or 

 less drooping lateral angles, but is always present when the oral aper- 

 ture is not short and roundish. Epistoma is most often more or less 

 hairy, sometimes rather densely, and it may be hairy all over or 

 only at the sides; sometimes it is very slightly hairy, and not rarely 

 it is quite bare; the colour is either quite yellow or with a more or 

 less complete black middle stripe, and also often with the lower side- 

 parts black; or it is of black or æneous colour; the colour and 

 hairiness of the epistoma is to some degree of systematic value; the 

 black epistoma may often be more or less pale pruinose. The jowls 

 are broader or narrower, in a few cases very narrow; they are 

 generally only slightly descending, but sometimes rat.her strongly 

 especially when the epistoma is descending; they are more or less 

 separated from epistoma, either there is a pit in front of them, or 

 there is a more or less complete dividing furrow; this furrow stretches 



