XVI. Prodrome of a Monograph of the Tabanid.e of the Uxited States. Part II. 

 The Genus Tabanus. By C. R. Osten Sacken. 



Read November 17, 1875. 



TABANUS. 



XhE total number of the hitherto described species of Tabanus from North America, 

 north of Mexico, is one hundred and two. Of these descriptions thirty-four have been 

 identified, and the names connected with tliem adopted in the present paper. Twenty-six 

 other species, aUhough identified, have been recognized as synonymous with previously 

 described ones ; and thus forty-two names remain as yet to be disposed of. It is very prol)- 

 able that among these forty- two names a very small number (perhaps not more than three 

 or four) represent species really unknown to me ; the large majority are either recognized 

 as doubtful synonyms of some of the identified species, or else they are unrecognizable, on 

 account of the insufficiency of the descriptions. 



Twenty species I describe as new ; not that I am convinced that none of them have 

 ever been described before, but because I could not recognize them with any reasonable 

 degree of probability among the forty-two unidentified species. The total number of spe- 

 cies of Tabanus from North America, north of Mexico, described in the present paper, is 

 thus brought to fifty-four. 



The tjxsk of the critic, as far as descriptions go, being nearly completed, the comparative 

 merit of the work of the different writers is brought out in a very striking light. Of 

 Wiedemann's more than twenty species (including those of Fabricius, which we know only 

 through Wiedemann), all but three are identified ; and of these three one is very probably 

 a species I do not know ( T. gracilis) ; the second ( T. nigripes) is as good as identified, and 

 the name is not adopted merely because another name, by Macquart, was preferred ; the 

 third is a very doubtful Fabrician species, belonging to a difficult group and described by 

 Wiedemann from a very imperfect specimen in Fabricius's collection {T. marrjinalis). 



As long as my materials were limited, the identification of several of Wiedemann's de- 

 scriptions remained doubtful ; when, among closely resembling species, I did not possess the 

 right one, I was sometimes led to identify a wrong one. But with the increase of material 

 these difficulties vanished, and even among closely allied species the right one was recog- 

 nized, thus showing the faithfulness of Wiedemann's work. 



Of Mr. Walker's twenty-nine species nineteen are unrecognizable to me, seven are syn- 

 onyms of other, mostly well known species, and only three are adopted. Among these 

 three I am not very sure whether T. catenatus Walk, should not be better called T. rece- 



MEUOIRS BOST. SOC. KAT. HIST. VOL. U. 106 (421) 



