DIPTERA. 351 



addition to the above, about six different forms of females have been seen, which I am 

 unable to assign a place. 



The total number of Mexican species recognized by me in the collection under 

 examination is twenty-nine, of which twenty-three are described as new. 



It will be understood that they all have black cilia to the tegulae, and four large 

 bristles on the scutellum. 



For P. dimidiatus, see the genus Gnamptopsilopus, infra, pp. 364, 365. 



The species described by Bigot (Ann. Soc. Ent. Fr. 1890) are scarcely recognizable, 

 and they are not included in the Table ; one only of them (Psilopodinus astequinus, 

 1. c. p. 290, and Bulletin, 1888, p. xxx) is from Mexico. The other unidentified 

 Mexican forms are mentioned by Osten Sacken, antea, p. 214. 



Table of the American Species o/Psilopus known to me, based on male specimens. 



1. Femora black 2. 



Femora yellow 35. 



2. Wings with dark markings 3. 



Wings without dark markings 22. 



3. Fore tarsi with a dense black fringe on the sides of the 4th and 5th 



joints ; middle tarsi with the 2nd and 3rd joints less broadly fringed 



(Mex.) bifimbriatus, sp. n. 



Fore tarsi of different structure 4. 



4. Fore tibiae black 5. 



Fore tibiae pale, at most somewhat brownish 9. 



5. Face with abundant, delicate, pale hairs (U.S.) [patibulatus, Say.] 



Face destitute of pale hairs 6. 



6. Second joint of antennae with numerous long bristles 7. 



Second joint of antennae with few and short bristles 8. 



7. Last four joints of fore tarsus short, subequal (W. U.S.) [pilicornis, Aldr.] 



Last four joints of fore tarsus decreasing in length (W. U.S., Mex.) . melampus, Loew. 



8. The brown cross-bands broadly connected on the fourth vein, leaving a 



round hyaline spot in the first posterior cell (Brazil) [guttula, Wiedem.] 



Cross-bands not connected behind; 5th joint of fore tarsus slightly 



compressed, with a silvery reflection on the inner side (Mex.) . . prtestans, sp. n. 



9. All the tarsi wholly black {guttula, Wiedem.] 



Fore tarsi wholly pale ; middle ones black, with a narrow silver fringe 



above on the last two joints (Mex., Brazil) diffusus, Wiedem. 



Fore and middle tarsi but little infuscated ; 4th joint of latter pure 



white, not enlarged (Antilles, Mex., Brazil) bellulus, Aldr. 



Fore tarsi infuscated, except part of the first joint 10. 



10. Knob of halteres infuscated 11. 



Knob of halteres yellow 16. 



11. Wings with only a faint cloud, before the third vein (Mex.) .... ciliipes, sp. n. 

 Wings with two cross-bands, or at least the hind cross- vein infuscated. 12. 



