DOLICHOPUS. 19 



tion of Dolichopus, in its present limited sense, was given by me 

 in 1857. Still, even now, this is one of the largest genera of this 

 family. Although possessing abundant and striking specific dif- 

 ferences, its numerous species show at the same time so much 

 agreement in their general organization, that a subdivision into 

 smaller genera is impossible at present, and in future an attempt 

 of that kind will require a great deal of caution. One is easily 

 tempted here to establish generic groups founded upon characters 

 of a purely specific value. The genus Rhagoneura, formed by 

 Rondani, is due to a mistake of this kind. To found a new genus 

 on D. ziczac, which species apparently requires it on account of 

 some differences in the neuration and in the structure of the an- 

 tennae, seems hardly worth while, as this is as yet the only species 

 showing such differences. 



The geographical distribution of the genus Dolichopus cannot 

 be inferred from the data found in older authors, as this genus con- 

 tained at that time very heterogeneous elements. Neither can Mr. > 

 Walker's superficial publications on exotic species be considered 

 in this respect as a source of information, as it is impossible to 

 tell from his descriptions which of his species belong to Dolichopus 

 in the restricted sense. Those species from the southern hemis- 

 phere, and fi'om the southern parts of the northern, which I had 

 occasion to examine at different times, proved not to belong to 

 Dolichopus in that sense. Hence we may safely conclude that 

 the genus Dolichopus, in the large majority of its species, belongs 

 to the cold and temperate zones of the northern hemisphere ; it 

 can, at least, be positively asserted that the number of species, in 

 Europe as well as in America, goes on diminishing toward the 

 South. 



The name of the genus (SOM^OJ, long, and rtov;, foot) has refe- 

 rence to the length of the feet of its species. 



Thirty-one North American species of Dolichopus have been 

 described by former authors ; some of them, however, do not belong 

 to this genus in the restricted sense adopted here. Of these 

 species three have been described by Say, one by Zetterstedt, one 

 by Macquart, and twenty-six by Walker. The descriptions given 

 by Mr. Walker are, for the most part, very bad, and the worst 

 are those published in the Diptera Saundersiana, as they con- 

 tain only such characters as are common to all the species, or at 

 least to entire groups, without paying the least attention to those 



