MICRODOT. 309 



completely discussed by Elditfc in 1845*. The curious larva) are 

 sliort-oval, very convex above, Hat below, with the marjiiu incised 

 to receive the head in front, and witli a posterior spiracular 

 process. They live in ants' nests. The larva) of J/. e;/r/eri have 

 been found frequently in nests of certain species of Formica in 

 stumps of coniferous trees, those of M. miUabUis in nests of 

 certain other species of Formica, usually under stones. Certain 

 non-European species have been discovered in nests of other ants. 

 Their exact relationship with the ants does not yet appear to be 

 certain. It has been suggested that they feed on the pellets 

 of food disgorged from the ants' mouths. The literature is 

 summarised by Lundbeck, Diptera Danica, v, pp. 579-581 (1916). 

 This well-marked genus forms a rather isolated group, its 

 nearest ally being, perhaps, Ceria. 



2\ihle of Sjiecies. 



1. '2m\ abdomiuiil segm«nit distinctly but not 



ureatly contracted ill middle, making the 

 abdomen appear siibchivate ; (vertex well 

 developed, scutellum small, rounded) . . 2. 

 2nd abdominal segment never contracted ; 

 abdomen short and rounded or elongate- 

 conical, never siibclavate -3. 



2. Legs orange : wings qnite clear ; 4th vein 



recurrent at a right iuigle contractus, sp. n., p. -'UO. 



Femora considerably black ; wings with 

 microscopic obvious ]iubescence ; 4th 



vein recurrent at an acute angle conveniens, sp. n., p. 311. 



3. Scutellum with hind corners produced into 



an obvious blunt point or tooth 4. 



kjcutelluin oblong or rounded, not produced 



into teeth 9. 



4. ]')rilliantly metallic species 5. 



Non-metallic Npecies ti. 



o. Abdomen without white hair-spots slilboides, Walk., p. 811. 



Abdomen with whita hair-spols nietallicus, de Meii., 



tP- •■•'-■ 



6. Small species, 5 mm. long cteruleus, Bruu., p. ;il.'>. 



Lar^'er species, 10 to 13 mm 7. [p. 313. 



7. .Vbdomeii mucii broader than 1 borax .... fulvopubescens, s\). r\., 

 .\bdomen not broader than thorax 8. [p. 314. 



8. Wholly black species carhonnrins, sp. n., 



Not wholly black s])ecie3 ajnformis, sp. n.. p. 314. 



9. Metallic species beilu.<<, sp. n., p. 310. 



Non-metallic species 10. [ p. 310. 



10. Surface of wing with microscopic .scaL;s . . KquamipenniR, .sp. n., 

 Surface of wing without trace <d' scales. ... 11. 



1 1. Abdomen in considerable part red 12. 



.Midomeu with no part red 13. 



Stelt. ent. Zcit. vi. p. 384, pi. i, fign. G-14 (184.")). 



