874 REPORT OF THE HARVARD AFRICAN EXPEDITION 
formly colored. Digitiform process of third antennal segment very slender. Length, 
LMS Tot VA NIM css cee & eecesed ote os nee ee ene] ce ee ee T. stimulans. 
3. Lower part of the face without a brownish black spot. First two abdominal tergites pale 
dirty yellowish, the second with a median dark brown triangular spot narrowly con- 
nected with similar lateral spots. Frons about four times as long as wide at the 
vertex, where it is distinctly narrowed. Length, 11.5 to 18 mm....... T. umbraticola. 
Lower part of the face with a brownish black spot. First two abdominal tergites pale 
dirty yellowish with narrow, darker, brownish hind margins............--+++++-> 
4. Basal division of third antennal segment more slender, the tip of the digitiform process 
not quite extending to the base of the second division. Frons about three and one- 
half times as long as wide at vertex, where it is scarcely narrowed. Length, 12 mm. 
Se ee ert ee ee eee pe ee ae EEN Te Pe TTT ee TA eo eS | T. concinna. 
Basal division of third antennal segment thicker, the tip of the digitiform process extend- 
ing well beyond the base of the second division. Frons about four times as long as 
wide at vertex, where it is distinctly narrowed. Length, 11 to 13 mm..... 7. mnotata. 
Tabanocella stimulans (Austen) 
Rhinomyza stimulans Austen, 1910, Ann. Mag. Nat. Hist., (8) VI, p. 354 (¢; Benue River, 
between Bagana and Lokoja, Northern Nigeria). Grinberg, 1913, Entom. Rundschau, XXX, 
p. 100 (9). Schouteden, 1929, Rev. Zool. Bot. Afric., XVII, 2, p. 240. 
Rhinomyza lutosa Grinberg, 1913, Entom. Rundschau, XXX, p. 100 ( 9; Bipindi, Cameroon). 
BEtG1an Conceo. — Lolo, Itimbiri River, one female (J. Rodhain). Medje, 
three females; Niangara, one female; Stanleyville, seven females and one 
male, as prey of Bembix bequaerti Arnold var. dira Arnold (H. Lang and J. P. 
Chapin). Macaco near Luebo, one female, October 1, 1921 (H. Schouteden). 
I have carefully compared the specimen from Macaco with the holotype at 
the British Museum. There is a good deal of variation in the extent of dark 
brown markings of the abdomen among these Congo specimens and some of 
the other characters likewise are rather variable. One may readily be tempted 
to describe some extreme individual variations as distinct species. Even the 
length of the upper apex of the second antennal segment does not appear to be 
fixed: some specimens have it very long and others much shorter; but there 
are intermediate examples and, moreover, these variations are not correlated 
with other differences. The extent of the infuscation in the apex of the anal 
cell is also subject to variation, but I do not believe it can be used as a specific 
character. 
In all the specimens listed above the dark median and apical bands of the 
wing are broadly connected along the costa, the hyaline triangle not extending 
into the marginal cell. This is however not the case in a female from Leopold- 
ville (J. Rodhain) and another from Lokandu (H. Schouteden), in which the 
hyaline triangle stops only a short distance from the costa. I cannot believe 
that this difference is of specific value. 
R. lutosa Griinberg is, in my opinion, a mere individual variation of T. 
stimulans, without trace of dark abdominal markings. 
T’. stimulans is a West African species known from Sierra Leone, the Gold 
Coast, Southern Nigeria, Cameroon and the Belgian Congo. Dr. Schouteden 
observed that it was attracted by light after dusk, at Lokandu. 
