DIOGMITES. 173 



DIOGMITES. 



Diogmites, Loew, Centur. vii. no. 36 (1866). 



(?) Deromyia, Philippi, Verh. zool.-bot. Ges.Wien, xv. p. 705 (1865). 



In my attempts to determine the species of this genus, I have taken into account, 

 almost exclusively, the described species from America north of Panama, and enume- 

 rated in my ' Catalogue of North-American Diptera' (1878). A good many species 

 from South America, belonging here, have been described by different authors ; these 

 are scattered in the genera Dasypogon, Saropogon, Seilopogon, Deromyia, &c. I deem 

 it, in most cases, impossible to determine such species from descriptions, especially 

 when the specimens to be determined are from a distant locality. For the North- 

 American species I have had the advantage of examining Dr. Loew's and Prof. Bellardi's 

 types ; by this means, if not attaining certainty, I at least increase the probability of 

 the correctness of my determinations. 



Further study, based on a larger number of specimens from different localities, will 

 perhaps reveal new and more precise characters for the definition of the species of 

 Diogmites. Those used up to the present time are not sufficient. The difference, for 

 example, between D. ternatus, Loew, and D. misellus, Loew, seems, on paper, clear 

 enough ; but, with the types before me, I remained uncertain to which of them to refer 

 certain specimens. I have great faith in Loew's eye for specific differences ; but these 

 differences must not only be felt, but defined, and in the above-quoted instance the 

 definition does not seem sufficient. The colour of the front end of the thoracic stripe, 

 the presence or absence of clouds in certain cells, and the colour of legs and palpi, are not 

 altogether " constant characters." In grouping specimens of Diogmites one is in doubt 

 whether to adopt a very large number of species or else to overlook apparently important 

 differences. I shall have occasion, in the sequel, to give utterance to many doubts of 

 this kind, and Prof. Bellardi has also expressed them in several passages (compare 

 this author's remarks about D. cuaitlensis, D. rubescens, D. pseudojalapensis, &c). 



The greatest difficulties are met with in the group with three distinct velvety-black 

 thoracic stripes on golden ground, comprising the species ternatus, Loew, misellus, Loew, 

 rubescens, Bell., affinis, Bell., dubius, Bell., jalapensis, Bell., and pseudojalapensis, Bell. 

 I believe that all these species are insufficiently defined. 



I retain here, as I did in my 'Catalogue of North-American Diptera' (1878), the 

 name given to this genus by Loew in preference to Deromyia, the date of which is but 

 one year earlier ; the latter applies to South-American species of a somewhat different 

 structure. In all the North-American species known to me the fourth posterior cell is 

 closed a considerable distance from the margin ; whereas it is open in Deromyia fuhipes, 

 Phil., and closed on the margin of the wing in D. gracilis, Phil. Should even the 

 generic identity be proved, Deromyia may remain as a subgenus ; but a change of name 

 in presence of such a difference in the typical species cannot, I think, be warranted. 



