148 . DIPTERA OF NORTH AMERICA. [PART II. 



This genus has been established by Mr. Haliday, and, in con- 

 sideration of the almost swordlike form of the antennae of the 

 species which became- first known, was called Machserium (from 

 tidzatga, the sword). As this same name has already been used for 

 a genus of plants, I have thought fit to abandon it and to substi- 

 tute the name of Smiliotus (from o^ixtwroj, the pruning-knife, 

 because the third joint of the antennas in the two known species 

 has the form of a pruning-knife). 



The two known species belong to the European fauna. 



Gen. XXII. APHROSYLUS. 



The known species of Aphrosylus agree in the following, in 

 part rather striking peculiarities which constitute the character of 

 this genus. The first joint of the antennae without hair, the 

 second of the usual transverse form, the third stalk-like and 

 pointed ; the arista entirely apical. The face narrowed above, 

 especially in the male. The proboscis turned towards the breast. 

 Palpi disengaged, hanging downward, in the male larger than in 

 the female. The abdomen of the male shows six segments ; the 

 short and rounded hypopygiurn ends it in the shape of a knob ; 

 its exterior appendages are elongated, parallel lamellae, fringed 

 with rather long hair. The female abdomen has only five seg- 

 ments. Wings of rather equal breadth ; the posterior transverse 

 vein is less distant from the margin of the wing, than its own 

 length ; the end of the fourth longitudinal vein is parallel with the 

 third. Feet with rather coarse bristles ; the first joint of all the 

 tarsi is much longer than the second ; the first joints of the hind 

 tarsi without bristles. 



The structure of the proboscis and the position of the palpi 

 distinguish the species of Aphrosylus sufficiently from all the 

 other genera of Doliclwpodidx. Hitherto only European species 

 have been described. 



The name of the genus (from a<}>pd$, the froth, and av^du, I rob) 

 has reference to the habit of these species to pursue their prey 

 along the shores of a surging sea. 



Gen. XXIII. THItfOPHILlIS. 



Character. The face in both sexes broad, not reaching as far 

 as the lower eye-corner, and ending below at an obtuse angle. 



