Prof. Aldrich on the DolicJiopodidse of St. Vincent. 309 



DOLICHOPODIDJE.* 



Of this family, the collection contains forty-six species, 

 of which five only can be recognized as previously 

 described. The study of so much material throws an 

 interesting light on the geographical distribution of the 

 genera. The entire absence of Dolichopus, of which the 

 continent of North America contains nearly a hundred 

 species, strongly emphasizes the fact that the genus is 

 limited to the temperate and colder regions. On the other 

 hand, more than half of the species in the present col- 

 lection belong to the group which may be termed the 

 Chrysotinse, embracing Chrysotus, Diaphoriis, and several 

 smaller genera, while this group is represented on the 

 continent by a considerably smaller proportion. 



The discovery of a second species of the peculiar genus 

 Polymedon, having identically the same habits as the 

 Californian species, is a matter of great interest. 



In the description of new species, the aim has been to 

 give a careful review of the generic as well as specific 

 characters in those not infrequent cases where there was 

 possibility of an erroneous generic determination. The 

 genera of Dolichopodidse are, at least in part, in need of 

 thorough revision, and several new ones must yet be 

 erected for North American forms. Unwilling to under- 

 take what should be the work of a more experienced 

 hand, I have avoided, as far as possible, the establish- 

 ment of new genera in the present article. 



I am under the greatest obligation to Professor 

 Williston, not only for the privilege of undertaking this 

 work, but for the use of books and other valuable 

 assistance. 



Gymnopternus. 

 Loew, Neue Beitr., v., 1857. 



1. Gymnopternus ruficornis, n. sp. 



^ . Face of moderate width, white pollinose ; front blue-greeu, 

 with white dust below ; cilia of inferior orbit white. Antennae 

 red, short, apex of third joint iufuscated, the dorsal arista slightly 

 pubescent. Thoracic dorsum bright green ; a blackish-bronze 



--• By Professor J. M. Aldrich. 

 TRANS. ENT. SOC. LOND. 1896. — PART III. (SEPT.) 



