Dec., 1904.] 
Tabanidae. 
243 
T. rhombicus has been misdetermined by many and conse- 
quently exists under various names in American collections. The 
specimens used in this study of the species were compared with 
Osten Sacken’s types and there are before me a long series of 
specimens agreeing with each of the three forms. Dr. John 
Marten has described some species of Tabanus in Vol. 14 and 15 
of the Canadian Entomologist, which seem to correspond with 
these forms, and after collecting all available information and 
studying Marten’s descriptions carefully, it appears to me that 
centron is the same as Osten Sacken’s second form of rhombicus, 
and as the latter author did not propose any name. Marten’s 
name remains valid. 
Tabanus rhombicus has the subcallus denuded and no stump 
on the anterior branch of the third vein. General color of the 
whole body dark with only a trace of red on the sides of the second 
and third abdominal segments and three rows of gray pollinose 
spots. Wings hyaline with traces of fuscous on the borders of 
the cross-veins and at the furcation of the third vein. Length 
13 to 15 millimeters. Specimens from Albam'- Co., Wyoming, 
collected by E. B. Williamson; from Estes and Manitou Parks 
Colorado, collected by Dr. F. H. Snow, and from southwestern 
Colorado, collected by E. J. Oslar. 
Therioplectes (?) melanorhinus Bigot seems to be this species, 
judging from the re-description of Bigot’s type Miss G. Ricardo 
has been so kind as to send me. 
Tabanus septentrionalis Loew. This species is somewhat 
variable in size and coloration but does not appear to be a diffi- 
cult one to recognize. The subcallus is not denuded; the gray 
triangles in the middle of the abdominal segments are united to 
form what may be called a dorsal stripe and on either side of this 
a prominent row of spots extends from the first to the sixth seg- 
ment, one spot to each segment. The ground color beneath 
these spots is often, but not always red.. The wings have a dilute 
yellowish tinge all over and the veins are brown but there is no 
distinct fuscous margins to the cross-veins or at the furcation of 
the third vein. Length 13 to 17 millimeters. 
Tabanus sequax Williston. The palpi are black, costal cells 
hyaline, and the stigma and margins of the cross veins and fur- 
cation of the third vein are also black. On account of the black 
palpi the species can only be confused with procyon, and the 
other characters mentioned will separate it from that. Length 
13 to 1C) millimeters. 
Thinking that Bigot’s leucophorus was this species, I sent 
specimens to Miss G. Ricardo who compared with the type and 
verified my determination. In her letter she makes the following 
statement; “The specimen sent on comparison with the tvpe is 
certainly identical ; the type is a trifle larger and the dark hairs 
