XVIJ Prodrome of a Moxograph of the Tabanid^ of the United States. Part II. 

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



Read November 17, 1875. 



TABANUS. 



J- HE total number of the hitherto described species of Tabanus from North America, 

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

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

 other species, although 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 prob- 

 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 ai'e 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 task of the critic, as far as descriptions go, being nearly completed, the comparative 

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

 Wiedemann's more than twenty sjjecies (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. nl(jr'q)es) is as good as identified, and 

 the name is not adopted merely because another name, hy 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. marginalls). 



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- 



MEMOIRS BOST. SOO. KAT. BIST. VOL. II. 106 (421) 



