40 D1PTERA OF NORTH AMERICA. 



it. Unfortunately most of them are founded on characters so va- 

 riable that they are of very little use, and it seems best to retain 

 the old ample genera. We feel the more compelled to do so, as 

 many species existing in N. A. cannot be referred to any of the 

 modern genera. 



The whole of the Ortalidce may conveniently be divided into 

 two sections : the first, which may be named TETANOPINA, has the 

 front more prominent, the face receding, the opening of the mouth 

 rather small, the clypeus less developed, and the proboscis less 

 thick ; in the second, the ORTALINA, the front is not prominent, 

 the clypeus very much developed, the opening of the mouth much 

 wider, and the proboscis much thicker. 



The N. A. Fauna possesses in PYRGOTA a genus of the first sec- 

 tion, particularly striking, and even somewhat deviating. Among 

 the other N. A. Ortalidce known to me there is only one species 

 belonging to CEPHALIA, whereas all the rest belong to the genus 

 ORTALIS, if we take it, as Meigen did, in a wider sense, and are 

 distributed especially among the genera Geroxys, Ortalis, Rivellia 

 and Delphinia, of modern authors. 



FAM. XLIY. TRYPETIDAE. 



Charact. Neuration complete ; the end of the auxiliary vein runs steeply 

 to the border of the wing and becomes obsolete ; first longitudinal 

 vein always with bristles, the third frequently, the fifth sometimes ; 

 two posterior basal cells rather large, the hindmost is often prolonged 

 to a point. Front on each side with two rows of bristles, one of 

 which is more above and interiorly, the other below and exteriorly. 

 Border of the mouth with no vibrissse. Clypeus none or rudimen- 

 tary. Proboscis never incrassated. Only the middle tibiae with 

 spurs ; all tibiae without erect bristle on the outer side before the 

 tip. Ovipositor horny, consisting of three elongated retractile 

 segments like the drawers of a telescope, the last of which ends in 

 a simple point. 



They are divided into two sections, DACTNA and TRYPETINA. 

 In the former the female abdomen, before the ovipositor, has ap- 

 parently only four segments, the fifth segment being diminutive 

 and entirely concealed under the fifth ; in the Trypetina the five 

 segments are all equally developed. 



As the Dacina, 'represented in Europe only by Dacus Olece, 



