OSTEN SACKEN ON WESTERN DIPTERA. 295 



B. Abdomen black, with white spots or cross-bands on the hind 

 margins of the segments : 

 (b) Legs reddish : 



10. profusus n. sp. ^ 9 . 

 (bb) Legs black : 



11. evidens h. sp. ^ 9 ; 12. rejectus n. sp. 9 ; 13. nngaior 

 n. sp. (<? ?) 9; 14c.positivus n. sp, ^ ; 15. sudatorn. sp.<? 9 . 



BB. Abdomen gray, with black spots : 



16. rattus n. sp. ^ 9. 



Aberrant species. 



17. cerussatus n. sp. ^ 9 ; 18. nebulo n. sp. 9 . 

 Analytical table for determining the species. 



' Antennal stylefuUy aslongas the third antennal joint ; wings with 

 distinct brown clouds on the cross- veins and on the bifurcation 



(1) <( of the third vein 18. nebulo u. sp., 9 . 



Antennal style much shorter than the third antennal joint ; wings 

 without distinct brown clouds, etc., (2): 



Third antennal joint red, (16) :, 

 Antennse altogether black, (3) : 



Hind tibise more or less red in the middle, (4) : 

 Hind tibise black, (9) : 



^ Male : front tarsi with a conspicuous dense fringe of silvery pile ; 



j two last joints of middle tarsi with a disk of black bristles; 

 (i\ J female: hind margins of abdonainal segments white on the sides 

 ^ ' [ only, sometimes very little, (7) : 



I Male : front and middle tarsi plain ; female : hind margins of 



1^ abdominal segments 2-5 altogether white, (5) : 



^ Scutellum convex, black; the brownish pollen at the base, if any, is 

 I hardly perceptible ; densely pilose with long, erect pile ; face in 



.p.s j the middle with white pile, (6): 



^ ' \ Scutellum flat, covered with dense gray pollen : longer hairs along 

 I the edge only ; face altogether with black hairs, 

 (^ 10. profusus n. sp. ^ 9 . 



C The fan-like row of hairs- in front of the halteres is black, 

 (6) ) 4. montanus Lw., $ 9 . 

 ( The fan-like row of hairs, etc., is white 5. leucozonus, Lw., ? . 



Scutellum shining black, (8): 



Scutellum with gray pollen 3. plausor n. sp., c? ? . 



c Abdomen with white pile on the sides ..1. calUpedilus Lw., ^ $. 

 (8) } Abdomen with black pile on the sides from the very base, 



I 2. cymbalista n. sp., $ 9 



Abdomen gray, with black, shining spots.. 16. rattus n. sp., ^ 9, 

 Abdomen black, with white cross-bands, (10) : 



i White cross-bands on the anterior margins of the segments, 

 (10) } 17. cerussatus n. si^., 3^ 9. 



( White cross-bands on the posterior margins of the segments, (11) : 



(2) { 



(3) I 



(T){ 



(9) { 



