422 C- K- OSTEN SACKEN'S PRODROME 



dens "Walk. ; T. fiilcesceus may be only a variety of T. bicolor Wied. ; and if I recognized 

 T. trljiincius, it is principally Ijecause I remembered having seen it in the British Museum. 



Macqnart's descriptions, although short, are more to the point than the unmenning de- 

 scriptions of Mr. Walker. But Macquart at different times worked in diiferent entomologi- 

 cal caljinets, without comparhig, or remembering, his former types ; thus he came often 

 to describe his own species again. Besides, he generally took but little trouble about iden- 

 tifying the descriptions of previous authors. Among the twenty-three species described by 

 him six are adopted, five are synonyms, and twelve are among the unrecognized and 

 doubtful.^ 



In adopting the species of former authors I have tried to hold the middle course between 

 too much confidence and too much skepticism. The latter is as injurious as the former, as it 

 leads to a new increase of synonymy. With the comparatively large material which I had, 

 besides the literal interpretation of the descriptions, a process of exclusion comes into play, 

 which reveals probabilities almost amounting to certainties. A description is referred to a 

 certain species, not because they exactly agree, but because no other species from the same 

 region is known that agrees lietter. 



During my journey to Europe, in 1859, I had an opportunity of seeing the Museums of 

 London and Paris, and to take a few notes, some of which I could turn to account now. 

 Unfortunately, my knowledge of North American Tabanidas at thnt time was very limited, 

 and thus the usefulness of a flying visit to those Museums was diminished in proportion. 

 About some of Wiedemann's types in the Vienna Museum I took the liberty of addressing 

 a few questions to Dr. Eedtenbacher, the Director of that Museum. His kind answers fully 

 confirmed the surmises I had ali-eady formed from Wiedemann's own descriptions, about the 

 identity of two or three doubtful species. 



By such means I hope, in the great majority of cases, to have avoided the two evils of 

 misapplying old names, or of unnecessarily introducing new ones. But should I even have 

 been occasionally mistaken, the evil is lessened by my having given full descriptions of all 

 the species, whether old or new. 



In describing, my only aim has been to enalde others to recognize the object described. 

 Tabani are variable in life ; they are still more variable in collections, according to the degree 

 of preservation of the specimens. I have purposely omitted statements which seemed 

 unnecessary for the practical aim I had in view, and 1 have purposely used vague expres- 

 sions, where any positive stateiuent would have been misleading. I am far from flattering 

 myself that in every single case my descriptions will be recognized, but I believe that the 

 possessor of a reasonable amount of material will be able to identify most of the species 

 with much less trouble now than before the publication of my i)aper. In the dilficult 

 groups of T. ahdominalis, tectus, varleycdus, of T. lonrjus, or of T. socius, sejitentnona- 

 lis, illotus, — groups containing either very variable species, or several closely resendjling 



» Summary of the critical review of N. A. species (north 1 Meigeii, 2 Wiedemann, 5 ]Macquart and 



of Mexico) described by former autliors: — 7 Walker). 



Identified and adopted 34 sjiecies. Unknown, doubtful, unrecognized or unrecog- 



(1 Linne, 1 Forster, 1 DeGcer, 5 Fabricius, nizable 42 species. 



3 Palisot, 9 Wiedemann, 2 Say, G JMacquart, (2 Linne, 1 Fabricius, 2 Wiedemann, 4 Pal- 



2 Kirby, 3 Walker, 1 Loew). isot, 1 Say, 12 Maccpiart, 1 Kondani, 19 



Identified and given in the synonymy . . . . 2C species. Walker). 



(1 DeGeer, 2 Drury, 4 Fabricius, 4 Palisot, Total . . . . 102 species. 



