Syrphidae. 1 9 



all ; in a few cases it is prolonged to a shorter or longer to very long, 

 styliform part, bearing the antennæ (quite strictly this part should be 

 considered as forraed partly of the frons, partly of epistoma); in the 

 males with touching eyes the frons is triangular, in the females and 

 in the males with separated eyes it is broad, more or less square. 

 The frons is more or less hairy, sometimes bare. The eyes are large, 

 oval, or in the males of a more or less reniform shape; they are 

 generally unicolorous, but in some cases they have dark spots, or 

 longitudinal or transverse bands ; they are bare or more or less hairy, 

 from almost imperceptibly to densely and long-hairy; sometimes they 

 show bands of denser hairs ; in some cases they are hairy in the male, 

 bare or almost so in the female. In the male the facets are generally 

 more or less enlarged on the upper part, sometimes slightly or almost 

 not; in a few cases the enlarged facets form a distinctly bordered 

 area. The antennæ are inserted more or less near to each other, 

 sometimes with a little distance, sometimes quite close; they are in- 

 serted on (or more strictly just below) the frontal prominence, in the 

 middle of the head or more or less above; more rarely they are 

 placed below the middle. The antennæ are, I think always, six- 

 jointed, the three last joints forming a three-jointed arista. The shape 

 of the antennæ are somewhat varying; the usual form belongs to the 

 disc and arista-type ; the basal joints are then more or less short, the 

 second somewhat compressed and with the apical margin prolonged 

 a little forwards on both sides, especially on the inside (somewhat 

 after the fashion in the Dolichopodids); the third joint in disciform, 

 roundish or more or less elongated oval, sometimes somewhat square, 

 and more or less compressed ; it bears on the dorsal side near the base 

 a shorter or longer, three-jointed arista, the basal joints of which are 

 quite small, generally only to be seen under the microscope and after 

 special preparation, as they are often more or less hidden in a hollow 

 in the third antennal joint, this is especially the case with the first 

 joint. From the mentioned shape the antennæ may then vary to 

 being longer, with the basal joints and especially the third joint 

 longer, and they may be rather long, with all three joints more or 

 less linear, and then the last joints slightly or not compressed, and 

 in a single case the two last joints form a spindle-shaped body; the 

 arista may be placed more outwards on the third joint, and in ex- 

 treme cases be terminal and take the shape of a style. The basal 

 antennal joints have small hairs and generally bristles at the apical 

 margin, especially above and below; the third joint is microscopically 

 hairy; in most cases the arista is likewise microscopically hairy, but 

 it may also be more or less distinctly short-plumose and in some 



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