1913] Alexander — New Neotropical Antochini 43 



running caudad; sides of the sclerite between the pseudosutural foves (humeral 

 pits) and the transverse suture, almost filled with a large rounded dark brown 

 spot, this mark not touching the dark median vitta (as in melanocephala) ; scutum, 

 with the exterior front angles darkened; scutellum and post-notum very dark 

 chestnut-brown. Pleurae, propleurse yellowish; mesopleurre very dark brown, 

 almost black. Halteres pale at base, stem brown, knob bright yellow. Legs: 

 coxas and trochanters bright yellow, abruptly contrasted with the dark pleural and 

 sternal coloring; femora light yellow, the apical portions abruptly dark brownish- 

 black, these dark tips rather broadest on the fore-femora; tibia dull yellow, the 

 extreme tip brown, broadest again on the fore-tibia; tarsi dark brown. Wings: 

 hyaline, stigma dark brown, square; wings broadly banded with pale greyish-brown, 

 the innermost band extending from the origin of Rs to the end of 2nd Anal, almost 

 diamond-shaped, the breadth sub-equal to the length; the middle fascia is a paler 

 continuation of the stigma, across the cord of the wing and ending at 1st Anal, 

 rather narrowest near the fork of M; the apical band is rather darker and fills out 

 the wing tip, its inner margin straight and embracing the outer end of cell 1st Mi. 

 Venation: (See fig. a.) : Cell 1st Mi very elongate, rather square at its inner end; 

 veins beyond cell 1st M 2 (discal) short, so that that portion of Mi + i between cross- 

 veins r-m and m, is longer than the distal segment of Mi+j. The type has the 

 cell 1st Mi open, confluent with cell Ms, due to the disappearance of the outer 

 deflection of vein M3. 



Abdomen: tergum dark brownish-black, the apices of the segments broadly 

 paler; 7th tergite orange-yellow; 8th blackish; valves of the ovipositor pale, 

 orange-yellow; sternum similar, but the pale apical margin even broader, em- 

 bracing the apical half of the sclerite. 



Holotype, 9 , Sonsonate, Salvador, Cent. Am. (Frederick Knab, Coll.) Para- 

 types, 9 9 . Aguna, Guatemala, Cent. Am. (alt. 2000 ft.) (Dr. G. Eisen, coll.) 



Type and one paratype in U. S. Nat. Mus. Coll. (No. 15,124). 



One paratype in author's collection. I take pleasure in naming this handsome 

 species after the "Father of American Dipterology," Baron C. R. von Osten 

 Sacken. 



This species falls in the polita group, the species of which may 

 be separated by the following key: 



1. Thoracic prsescutum entirely shiny black 2 



Thoracic prsescutum more or less orange-yellow or brownish 4 



2. Pronotum yellowish. (Colombia) trifasdata End 1 



Pronotum black 3 



3. Small species ( c? , length, 2.5-3 mm. ) ; legs with the basal two-thirds 



yellowish-tawny. (Brazil) polila O. S.» 



Larger species ( 9 , length, 5 mm.); leg dark brown. (Costa Rica) . .rostrata End.* 



lEnderlein, Zoolog. Jahrbuch abth. f. Syst.; vol. 32, pt. 1; p. 69, 70; fig. Ri (1912). 



2 Osten Sacken, Berl. Ent. Zeitschr.; vol. 32, pt. 2; p. 189 (1887). 



sEnderlein, Zoolog. Jahrbuch abth. f. Syst.; vol. 32, pt. 1; p. CS, G9; fig. Qi (1912). 



