426 C. R. OSTEN SACKEN'S PRODROME 



Attlotus.^ Eyes pubescent, no vestige of an ocellar tubercle ; frontal callosity wanting 

 in the two American species (or small and rudimentary, in the European species) ; head 

 rather large, very convex anteriorly, and rather concave posteriorly ; difference m size be- 

 tween the large and small focets in the male considerable, line of division between them 

 very distinct (even in dry specimens) ; palpi (?) stout at base ; upper branch of the third 

 longitudinal vein knee-shaped at base (emitting a stump of a vein in the European species); 

 first posterior cell broadly open ; coloration of the eyes imiform (sometimes a single indis- 

 tinct stripe). The coloring of the eyes I quote after European authors ; I do not know 

 that of the American species, Ijut have little doubt, from the appearance of the dry speci- 

 mens, that it is the same as in the others. 



The next relative of Atylotus in North America would be T. tnexlcamts, which is very 

 nearly an Atylotus with glabrous eyes. And again the gi'oup of T. cosfalis, nigro-vittatus, 

 fulvulus, sagax, with their stout palpi, broadly open first posterior cell, green eyes, some- 

 what knee-shaped basis of the upper branch of the third longitudinal vein, etc., seems like- 

 wise to be related to Atylotus. 



Of the total number of North American Tabani described by me, only two ( T. ininctlfer 

 and T. rhombims) belong to the region beyond the western plains, and therefore fifty-two 

 inhabit the region east of the plains, that is, the valley of the Mississippi, the Atlantic 

 States and the British Possessions. The fauna of this region, especially of the Southern 

 States, is fiir from being exhausted, and the number of species will certainly reach far be- 

 yond sixty. At present I know already about half a dozen species, which I have seen in 

 collections and have not introduced in this paper, not wishing to describe new species in 

 this difficult genus from single specimens, except in cases where a species is as striking as 

 T. cyviatophorns, and where the s-j:)ecimen was uncommonly well preserved. Twentv-four 

 species I know to occur in the New England States alone, and even this number will un- 

 doubtedly be increased. For comparison's sake I will state that Zetterstedt has twenty- 

 four species for Sweden, Norway, Denmark and Finland ; Schiner thirty-two for Germany 

 and Austria ; Zeller thirteen for Silesia. As yet not a single species of Tabanus common 

 to Europe and North America has been ascertained to exist, although some of the northern 

 species of the group Therioplectes come very near to European species (for instance, my 

 T. socius to T. trojncus). It is not improbable that with a better knowledge of that group 

 some cases of undoubted identity will be disclosed. 



All the original specimens of my descriptions, as well as all the varieties and aberrant 

 specimens mentioned in my text, are to be found at the Museum of Comparative Zoology, 

 in Cambridge, Mass. The most important contributions from abroad I received from the 

 Entomological Society in Philadelphia, and from the Detroit Scientific Association ^ ; for both 

 of which I return my sincere thanks. 



OBSERVATIONS ABOUT THE ANALYTICAL TABLE OF THE SPECIES. 



1. As the pubescence of the eyes, in female specimens especially, is sometimes very 

 difficult to perceive, either being naturally scarce, or worn off, I have introduced the ocelli- 

 gerous tubercle as an auxiliary character. I know of no North American Tabanus Avith a 

 distinct ocelligerous tubercle and, at the same time, with glabrous eyes in both sexes ; so 



l'Aj-(';i(j-of, without callosity. " Diptera collected in Florida, by Messrs. Hubbard and 



Schwarz. 



