OSTEN SACKEN ON WESTERN DIPTERA. 255 



terior cell open, no pulvilli, the first antennal joint much shorter, for an 

 antennal style a mere bristle, the beard less long, etc. Comparatively, 

 the head of Pantarbes is larger and broader, the body is stouter, the 

 prsefarca shorter. 



Head large, considerably broader than the thorax ; vertex in the male 

 equal in breadth to about two-thirds of the greatest horizontal diam- 

 eter of the eye, still broader in the female 5 the front immediately above 

 the antennae is about three times as broad as the vertex (in the male), 

 the eyes being placed obliquely; front and face descend nearly perpen- 

 dicularly toward the oral margin, the antennae, therefore, inserted at a 

 much lower level than the vertex. The lower part of the front, the 

 face, the base of the antennae, and the oral opening are entirely con- 

 cealed from view by a dense tuft-like crop of hair, occupying the whole 

 anterior part of the head, and similar to that of Anastcechus. Those 

 parts of the head can only be examined after the removal of this hair. 



Ocelli placed on a hardly perceptible flat prominence of the vertex ; 

 the lateral ones large, and at a distance from each other, which, in the 

 male, is at least by one-half larger than the interval between each of 

 them and the nearest orbit of the eye ; in the female, the latter interval 

 is a little larger than the distance between the ocelli. 



Antennce inserted at a distance from each other which is but little 

 shorter than the breadth of the vertex in the male; first joint (con- 

 cealed in the facial tuft of hair) nearly cylindrical ; second joint short, 

 not longer than broad; the third a little longer than the two first taken 

 together, slender, beginning by a short basal expansion, then attenuated 

 for about one-third of its length, and then again very slightly expanded, 

 with but a small attenuation toward the end; at the tip, a minute, stout, 

 cylindrical, 2-jointed style, with a microscopic bristle on top ; the style 

 when viewed from above the vertex is somewhat at an angle to the 

 rest of the antenna. 



Eyes glabrous ; the passage from the larger facets above to the smaller 

 ones below in the male is gradual ; in dry specimens, at least, the line 

 of separation is not visible. 



Oral opening comparatively small, its upper edge reaching but little 

 above the lower corners of the eyes. 



Proboscis porrected forward, comparatively short, projecting but little 

 beyond the tip of the antennae, not tapering toward the end. 



Thorax of moderate size, not gibbose, nearly on a level with the head. 



Scutellum small in comparison with those of Bombylius and Systcechus. 



Abdomen a little longer than thorax and scutellum together, as broad 

 as the thorax at the base, and gradually tapering toward the tip. 



Legs, especially the femora, comparatively strong; first tarsal joint a 

 little shorter than the four others taken together; ungues curved; pul- 

 J villi distinct and long. 



Venation of the icings : first posterior cell closed ; its petiole as long 

 as in an ordinary Bombylius; second vein gently arched before the cross- 



