DIPTEEA. 



J45 



infuscated, the last joint on the inner side below with three or four minute, but stout, black bristles ; 

 the inner claw bends back towards these, so as to form the beginning or rudiment of a grasping- organ, 

 which is less fully developed than in S.falco and 8. similis. Middle coxae with a row of five stout, blunt, 

 black bristles on the front side (a close inspection under the compound microscrope indicates that these 

 are really located on a horn- or scale-like projection from the basal part of the coxa, which extends 

 parallel with the body of the segment). Middle and hind tarsi slightly infuscated. Middle and hind 

 femora each with a distinct row of stout hairs below, largest on the latter. Wings subhyaline, quite 

 short ; the fourth vein ending almost immediately behind the apex. 

 Length 1/7 millim. 



Hab. Mexico, Teapa in Tabasco (H. H. Smith). 



One male. This species, with S. falco and S. similis, should constitute a separate 



genus. They all agree in having a short compact form, entirely unlike that belonging 



to Sympycnus. The thick, short, and very unsymmetrical hypopygium is also different. 



8. coxalis is readily separated from the other two species mentioned by its yellow 



ntennse. 



DIAPHORUS. 



Diaphorus, Meigen, Syst. Beschr. iv. p. 32 (1824) . 

 Lyroneurus, Loew, Wien. ent. Monatschr. i. 37 (1857). 



1. Diaphorus simplex. 



Lyroneurus simplex, Aldrich, Trans. Ent. Soc. Lond. 1896, p. 333, t. 12. fig. 117 \ 



Hab. Mexico, Orizaba, Mexico city, Atoyac, Teapa (H. H Smith).— Antilles, 

 St. Vincent \ 



Numerous specimens. I find that the female of this species cannot be distinguished 

 from the same sex of D. spectabilis, and the genus Lyroneurus is therefore, in my 

 opinion, untenable. 



2. Diaphorus spectahilis. 



Diaphorus spectabilis, Loew, Neue Beitr. viii. p. 57 l ; Mon. N. A. Dipt. ii. p. 162 2 . 

 Diaphorus approximates, Aldrich,, Trans. Ent. Soc. Lond. 1896, p. 321 3 . 



Hab. North America, United States l 2 . — Mexico, Cuernavaca, Sierra de las 

 Aguas Escondidas, Orizaba, Vera Cruz, Atoyac, Medellin, Teapa (H. H. Smith). — 

 Antilles, St. Vincent 3 . 



A large number of specimens. In this species there appears to be an occasional 

 variation in the degree of contiguity of the eyes of the male : Loew l described them 

 as " meeting upon the front to a large extent." In the St. Vincent examples the eyes, 

 normally, are not quite contiguous, and I described the species under a new name ; but 

 I ascertained afterwards that this was also the case in the specimens inhabiting the 

 United States. Amongst the Mexican insects before me, one male has the eyes 

 narrowly, and another has them rather widely, separated, although in the latter there is 



biol. centr.-amer., Dipt., December 1901. 2 y 



