408 PROCEEDINGS OF THE NATIONAL MUSEVil. vol. 46. 



Since then some species have been characterized, and in addition cer- 

 tain of the older species described in Tabanus can be referred here 

 with certainty. One specimen before me proves to belong to an 

 undescribed species. Brethes has referred to Stibasoma Macquart's 

 Tabanus fenestratus, but, as it would seem, wrongly.^ None of the 

 characters peculiar to the genus are mentioned by Macquart, and his 

 figure shows the antennae without the characteristic long process on 

 the third antennal joint and no ciliation on the hind tibiae .^ Whether 

 Professor Brethes had another species before him or a A\Tong concep- 

 tion of the genus does not appear. 



A series of five specimens of Stihasomafulvoliirtus before me, taken 

 by Prof. F. W. Urich, in Trinidad, makes it evident that the colora- 

 tion of the vestiture, which is given primary importance in the sepa- 

 ration of the species by Miss Ricardo, is subject to considerable varia- 

 tion, and therefore unreUable. This will appear from the notes which 

 follow under some of the species. The wing coloration appears to be 

 the most constant color-character, and therefore is employed as far as 

 possible in the following table: 



TABLE OF THE SPECIES. 



1. Wings in great part black 2 



Wings not black 7 



2. Wings pale at extreme tip, but without pale discal spot 3 



Wings with a pale discal spot 4 



3. Body entirely black willistomi Lutz. 



Abdomen with a yellow basal band theotsenia (Wiedemann) . 



4. Discal spot extending to costa, yellow flavistigma Hine. 



Discal spot not extending to costa 5 



5. Wings with discal spot ''lurid " mallophoroides (Walker). 



Wings with discal spot clear 6 



6. Clear spot restricted to discal cell festivus (Wiedemann). 



Clear spot extending into second basal cell. dyridophorum, new species. 



7. Wings clear, with two dark bands pachycephalum Bigot 



Wings yellow and gray 8 



8. Wings yellow, gray on apical third tristis (Wiedemann). 



Wings gray along posterior margin 9 



9. Body black, a yellow basal patch at sides of abdomen bicolor Bigot. 



Abdomen banded 10 



10. Wings gray, yellow at base and anterior margin dives (Walker). 



Wings yellowish, gray at tip and along posterior margin. fulvohirtus (Wiedemann). 



STIBASOMA WILLISTONU Lutz. 

 Stibasovia tJieotaenia Williston (not Wiedemann), Kans. Univ. Quart., vol. 3, 



1895, p. 194. 

 Stihasoma willistonii Lutz, Centralbl. Bakt., Abt. I, Orig., vol. 44, 1907, p. 143. 



This species differs from theotsenia by the absence of the yellow band 

 at the base of the abdomen. Williston had a single male, and suppos- 



1 AnaL Mus. Nac. Buenos Aires, ser. 3, voL 13, p. 475, 1911. 

 3 Dipt, exot., vol. 1, part 1, p. 135, pi. 16, figs. 3, 1838. 



