DIPTERA OF NORTH AMERICA. [PART II. 



The few species of Achalcus as ^et known, belong all to the 

 European fauna. 



Gen. XXXIX. MEDETERUS. 



Characters. Face of both sexes rather broad, and in both with 

 a transverse swelling below its middle. The proboscis very much 

 swollen ; when in repose, both sides of its opening are so close 

 together, that its lower surface forms but a single convexity. The 

 first joint of the antennae glabrous, the third rounded or somewhat 

 ovate, with a slender apical or subapical arista. Eyes not hairy. 

 The upper side of the thorax on its posterior end with a concave 

 declivity. The hypopygium with a short peduncle, entirely dis- 

 engaged, inflected under the venter, with rather short appendages. 

 Feet rather long and slender, almost entirely without bristles ; the 

 first joint of the hind tarsi without bristles, shorter than the second. 

 The third longitudinal vein, in most of these species, ends not far 

 from the tip of the wing, and the last segment of the fourth longi- 

 tudinal vein converges towards the third. 



The genus consists of two groups ; the first of these differs from 

 the second by the shorter distance of the posterior transverse vein 

 from the margin of the wing, by a stronger convergency of the 

 third and fourth longitudinal veins, by the smaller length of the 

 first joint of the hind tarsi and a more slender structure of the 

 body. 



The name of Medeterus (from ^fo'tspoj, neither of the two) was 

 given to this genus, because its species could not be located in any 

 of the two genera of Dolichopodidae, established -at that time. 



The known species belong to Europe, Northern Asia, North- 

 ern Africa, and North America. Of the latter I possess un- 

 fortunately only fragments of specimens, so that my statements 

 about them will necessarily be very imperfect. 



1. M. ni gripe 8 LOEW. 9 Nigricans, antennis pedibusque concolori- 

 bus, thoracis dimidio anteriore albido-bivittato, dimidio posteriore et 

 scutello albido-pollinosis, alls subhyalinis. 



Blackish, antennae and feet of the same color, the anterior part of the 

 thorax with two whitish stripes, the posterior half and the scuteilnra 

 covered with whitish dust, wings rather hyaline. Long. corp. 0.12. 

 Long. al. 0.12. 



SYJJ. Medeterus nigripes LOEW, Neue Beitr. VIII, 73, 1. 



