INSECUTOR INSCITI^ MENSTRUUS 95 



mens. In fact, the species in general habitus is distinctly a 

 Phalacromyia rather than a Volucella, if, indeed, the two genera 

 can be held separate. Unless the genera can be redefined on 

 characters other than wing-venation, it would seem advisable, 

 in view of this variation, which may also occur in other species, 

 to merge the two genera. 



WHAT IS TABANUS MEXICANUS? 



(Diptera, Tabanidcc) 

 By FREDERICK KNAB 



Under the name Tabamts wiexicanus modern systematists 

 have confused a number of distinct forms. Most of these 

 were recognized and described as distinct by the early authors, 

 but since then have been generally considered as variants of a 

 single species. It is true, these forms agree closely in struc- 

 tural details and coloration, and a hasty examination would 

 easily lead to the conclusion that they are conspecific. Never- 

 theless they are distinct, as the writer hopes to show. 



A considerable material is before the writer and this repre- 

 sents three distinct forms, now confused under the oldest spe- 

 cific name, niexicanus. These three forms agree closely in 

 size, in the pale green color of the body, legs and wing-stigma 

 (usually changing to yellow or brown after death), the nar- 

 row frontal stripe without differentiated frontal callosity, the 

 shape of the antennae, and other details. The wing-venation 

 also agrees very closely in the three forms, the first posterior 

 cell being wide open and the upper branch of the third vein 

 with a very short appendix, this latter altogether obsolete in 

 many specimens of one of the species. The obvious differences 

 are in the wing-coloration, two of the forms having the wings 

 spotted in a different manner, while the third has them wholly 

 unspotted. 



The true iiiexicamts of Linnaeus, described from South 

 America, be it noted, has the wings mottled with sharply de- 

 fined black dots disposed in the manner described below. A 



