3. ATHERIX 289 



" forked tail about one-third of the length of the body, and has the power 

 " of raising itself in the water by an incessant undulating motion in a vertical 

 " plane." It is recorded from all Europe and extends to Siberia and Japan. 



Synanymy. — Sylvicola melancholia of Moses Harris is evidently this species, but 

 I do not feel inclined to resurrect that name. 



2. A. marginata Fabricius. Wings blackish with conspicuous clear 

 markings. Legs wholly black. 



A very distinct fly, obviously related to A. Ibis but smaller, 

 blacker, and narrower. 



^ . Face and frons blackish, but the epistoma and the side-cheeks bearing greyish 

 dust ; frons with numerous extra long but not dense thin black hairs which 

 are continued up between the eyes quite to the ocellar space and which leave 

 only a very slight gap before the similar pubescence on all the vertical part ; 

 epistoma quite bare, slightly channelled, fairly large, occupying distinctly 

 more than half the space between the eyes ; side-cheeks (narrower than 

 in A. Ibis) bearing long pubescence similar to that on the frons, and this 

 pubescence extending beneath the eyes to half- 

 way up the back of the head, but on this latter 

 part becoming shorter, more irregular, and separ- 

 ated from the eyes by a narrow bare space ; 

 jowls rather small, but the lower half of the back 

 of the head considerably puffed out, and all this 

 part of the head has a grey ground colour; the 

 actual back of the head and the under part to 



the back of the mouth clothed with long thin dull pm^ igi.—Athenx marginata 



whitish hairs j upper part of the back of the head 6- x 43. 



reduced until it does not protrude behind the eyas, 



black with abundant short black bristly hairs which form no ciliation and 

 which are abruptly contrasted with the long hairs on the vertex. _ Proboscis 

 long, protruded, black, with inconspicuous short black hairs which become 

 rather crowded about the tip ; palpi long, being as long as the proboscis, thin 

 and almost pointed, strongly upcurved on the basal two-fifths, black with 

 a tinge of grey and bearing numerous conspicuous long black hairs. Antennae 

 (fig. 191) dull black, shaped as in A. Ibis but with the arista rather longer 

 and bearing some sparse microscopical pubescence. 



Thorax and scutellum shining black with no trace of any markings unless 

 the humeri and the space behind them show a greyish tinge, and this colour 

 increases until the pleurae become entirely covered with close grey dust ; thorax 

 bearing all over the disc equally long but not dense black hairs, and the 

 scutellum bearing similar but longer hairs ; pleurae with whitish grey 

 pubescence on the upper hind part of the mesopleuras, on the prothorax 

 and space above, and on the metapleurae, while the sternopleufa^ (though 

 apparently bare) have a faint pale pubescence on their upper part and a 

 few very short scattered black bristles on their lower part. 



Abdomen black with the sides of the basal segment grey, and (when viewed 

 from above sideways) with fairly well-defined entire grey hindmargins to the 

 segments, though when viewed quite from above showing large vague tri- 

 angular grey spots on the sides and narrow grey side-lines on the hindmargins 

 of the segments which nearly meet on the third segment and which do meet 

 on the fourth and fifth segments. Pubescence fairly long, rather erect and 

 conspicuous though not dense on the sides of the four basal segments, but 

 shorter (though not very short) denser and black on the disc and on the fifth 

 and sixth segments. Belly entirely covered with grey dust and bearing 

 rather sparse pale pubescence. Genitalia very long and large, bearing 

 pale pubescence beneath. 



Legs wholly black, though the coxae may be rather greyish ; relative 

 lengths of tibi^ and tarsi as in A. Ibis. Pubescence all black, except for 

 a few grey hairs on the hind coxae and numerous pale hairs above the basal 



T 



