Descriptions of British Diptera. 149 



the males with yellow pubescence, and a yellow circle round the eyes ; 

 the hypostome yellow in the females, with a dark line down the middle; 

 forehead black and shining, the hinder part of the head yellow: thorax 

 dark-brown and unspotted, clothed with light brown hairs ; scutel- 

 lum yellow, with a triangular black spot at the base, the spines fre- 

 quently tipped with the latter colour : abdomen considerably wider 

 than the thorax, pubescent, and of a deep black above, the second, 

 third, and fourth segments, having a triangular spot of citron-yel- 

 low on each side, the anterior pair large and triangular, the others 

 narrower and more elongate ; the anal segment with a triangular 

 spot of the same colour in the centre : on the under side, the abdo- 

 men is dull yellow, with a narrow oblique black streak on both sides 

 of the second and third segments, sometimes united into a continu- 

 ous band on the latter, and the terminal segment edged with black : 

 the scales at the base of the wings and the halteres yellow, the 

 wings pale brown, the principal nervures inclining to ferruginous ; 

 legs nearly of the latter colour, the thighs brown except at the base. 

 Length 7|— 8 lines. 



The chamseleon fly was so named by Goedart, because he 

 found that it could subsist a very long time without food, a proper- 

 ty for which that animal was long considered famous. It is not so 

 often met with in most parts of England and Scotland as some of 

 the following species, but it may be found occasionally throughout 

 the summer by the sides of ponds and in marshy situations, hovering 

 about the flowers of Caltha palustris and other marsh plants. Sides 

 of Duddingston Loch, Braid marshes, and other similar places round 

 Edinburgh, but not frequent. " CardewMire." — T. CHeysham,Esq. 



2. Stratiomys Potamida. 



Meig. Zweiflugeligen Insecten, Vol. iii. 137 — Stratiomys Potamida, Ste- 

 phens's Cat. No. 8469. 



About the same size as the preceding, to which it bears so close 

 a resemblance that it might readily be taken for a variety ; it is 

 Meigen's opinion, however, that it is decidedly distinct, as indicated 

 by the following characters : the scutellum, instead of having a tri- 

 angular spot at the base, has a black band, continued across the sur- 

 face and turned over the sides ; the scutellar spines always entirely 

 yellow ; the second segment of the abdomen bears two lateral trian- 

 gular spots, as in S. charnceleon, but on the hinder margin of the 

 third there is a yellow band, narrow and continuous in the female 

 broader and interrupted in the male ; the fourth segment with an en- 

 tire band in both sexes ; anal segment with a yellow triangle : un- 

 der side of the abdomen yellowish, with four narrow black bands the 



