ORTALIDiE — SYSTEMATIC DISTRIBUTION. 49 



metathoracic bristle, from the Ortalina, in the absence of the 

 prothoracic one. With the former it moreover agrees in the 

 larger size of the oral opening, the greater development of the 

 clypeus and the stouter proboscis ; with the latter it has the 

 more or less distinct development of the fifth segment of the 

 female abdomen in common. While some of the genera show a 

 very close affinity to the Platystomina in general appearance, 

 others stand as near to the Ortalina, so that the Cephalina seem 

 to form a transition from the first to the second of those sections. 



The genus Cephalia, introduced by Meigen, shows some 

 affinity to those genera of Platystomina, the species of which are 

 distinguished by their slender shape, especially to the genera 

 Mischogaster and Myrmecomyia. It necessarily must be con- 

 fined to those species which, like the typical Cephalia rufipes 

 Meig., have a mesothoracic bristle. The species added later to 

 it, although in their general shape and their coloring they more 

 or less resemble the true Cephalise, do not show the necessary 

 agreement with them in those characters which are the most 

 trustworthy in the establishment of the genera of Ortalidse. They 

 belong in the group Platystomina and principally in the genus 

 Mischogaster, in part also in the genus Myrmecomyia. The 

 genus Cephalia, in this narrower sense, does not contain as yet 

 any American species. As, for this reason, I will have no occa- 

 sion to refer to it again, I will characterize it here : — 



Body slender, abdomen narrow at the basis, its first segment 

 without any knot-shaped swelling ; feet rather long and slender. 

 Hairs on the body extremely short; thorax with a few small 

 bristles on the lateral and the posterior portions only ; the bristles 

 before the scutellum and its own lateral bristles are very short. 



Antennae long and slender; their second joint short. Face 

 shield-like, convex, without antennal foveas. 



Palpi very broad ; proboscis rather stout and mentum some- 

 what swollen. 



Wings attenuated towards the basis in the shape of a wedge, 

 with a very narrow alula; the second longitudinal vein hardly 

 sinuose at all ; the third and fourth longitudinal veins normal in 

 their course ; the anterior basal cell of equal breadth ; the first 

 longitudinal vein bristly towards its end only; the crossveins 

 rather distant from each other ; the picture of the wings usually 

 4 



