138 DIPTERA OF NORTH AMERICA. [PART JII. 



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which seem to be rather constant in their position, but less con- 

 stant in their extent; the figure is drawn from a female specimen, 

 which has them less extended ; usually, the inside of these spots 

 is distinctly paler, but this varies in different specimens; very 

 characteristic is the part of the picture surrounding the small 

 crossvein, which does not seem to be subjected to any important 

 variation. 



Hab. New York (A. Fitch). 



Observation. — The described specimens, a male and a female, 

 were obtained by Baron Osten-Sacken from Dr. Eitch under the 

 name of Trypeta corticalis. 



4. S. vau Say. 9.— (Tab. VIII, f. 29.) Fusco-nigra, polline albo- 

 cihereo aspersa, punctis maculisque fusco-nigris variegata ; alae hyalinae, 

 maculis octo nigris. quatuor costalibus, unica apicali, unica margini 

 postico contigua reliquis majore et venam transversalem posteriorem 

 includente, duabus denique minoribus vena? longitudinali sextae appo- 

 sitis; praeterea macula ovata lutescens perinagna, a mucula costali 

 secunda usque ad secundaria venae sextae maculam pertinens conspicitur 

 et macula costae tertia eodem colore luteo cum macula marginis postici 

 conjungitur, ita ut fascia integra, in media ala multo dilutior, appareat. 



Brownish-black, powdered with whitish-gray, marked with brownish-black 

 dots and spots ; wings hyaline, with eight black spots, four on the costa, 

 one at the apex, one, larger than the others, near the posterior margin, 

 covering the posterior crossvein, two .smaller spots upon the sixth 

 longitudinal vein; besides, there is a very large ovate, brownish-yellow 

 spot, extending from the second spot on the anterior margin to the 

 second of the two smaller spots on the sixth longitudinal vein ; the third 

 spot on the anterior margin is connected by the same coloring with the 

 spot upon the posterior crossvein, thus forming a complete crossband, 

 which is much paler in the middle of the wing. Long. corp. 0.16 — 0.19 ; 

 cum terebra 0.18—0.24; long. al. 0.14—0.18. 



Syn. Ortalis vau Say, Journ. Acad. Phil. VI, 184, 4. 



Ground color opaque brownish-black. Head of the same color, 

 but the anterior portion of the front and the face of a reddish- 

 brown or dirty brick-red coloring, which sometimes also extends 

 to the middle line of the front. The two superior hairs upon the 

 lateral margin of the front are bristle-like. The front, from the 

 anterior margin nearly as far as the ocelli, is clothed with black 

 hairs, inserted upon impressed punctures ; there is no definite 

 picture upon it. The thorax is covered with a white pollen and 

 punctate with brownish-black. The picture on the thoracic 



