22 Mr. C. IT. T. Townsend on Diptera 



brown, tl)e labella sliinino; dark brown. Face, thorax, and 

 scutellum brassy-yellow pollinose ; abdomen shining tawny 

 yellow, the apical portion (in the dried specimen) slightly 

 tinged with brownish, but yellow in life. Knobs of halteres 

 greenish ■ yellow. Eyes bare, contiguous from the small 

 tubercle-like yellow vertex to near base of antenna?, leaving 

 a small, bare, brassy-yellow pollinose frontal triangle, the 

 upper angle abruptly tapered and acute. Anterior branch of 

 third vein with a long stump at its basal angle, the stump 

 being three times or more the length of basal section of branch. 

 Wings, except costal border above mentioned, pure hyaline, 

 wholly without sign of spots ; veins yellow. The yellow of 

 costa reaches from the elongate slightly oblique stigma, which 

 is more deeply yellow, to base of wing, filling out the portion 

 basad of the basal cells with a tinge of the yellow. Posterior 

 cells all open, none of them narrowed, except that fourth is 

 narrowed a little on border from its greatest width in middle. 

 Difference in size of facets of eye marked, abrupt ; the small 

 facets extend up to a little short of the anterior or inner angle 

 of eye, but the line of separation extends backward from this 

 point at a slight upward angle off the horizontal. In life this 

 specimen had little of the green tinge, except on the eyes as 

 described. 



I give this full description of this very handsome variety 

 of a well-known species, because existing descriptions of the 

 species are lacking in detail. The points of difference 

 between this variety and the typical form, as well as several 

 other varieties of mexicanus, are given in the table below. 



A considerable number of forms of this group have been 

 described by various early authors — Fabricius, Meigen, De 

 Geer, Beauvois, Macquart, and Walker — and classed as 

 synonyms of mexicamis (see Osten Sacken, Cat. p. 59). The 

 typical form has the wings spotted witli brown. Only one of 

 the others has the wings absolutely unspotted, namely, 

 inanis, Fabr., which I consider a good variety on this 

 character. It is at once distinguished from Jhnonus by the 

 tomentum being wholly cinereous instead of yellow. These 

 forms should be separated as follows : — 



Table o/'Tabanus mexicanus and Varieties. 



1. Wings spotted 2. 



Wings wholly without spots 4. 



2. Spots only on cross-veins and bifurcation 



of third vein 3. 



Spots _ also on margin of wing at ends of 



longitudinal veins ulivaceiis, De G. 



(S. America.) 



