PROC. ENT. SOC. WASH., VOL. 20, XO. 9, DEC., 1918 205 



forms almost a semicircle. In T. abdominalis, however, (as 

 designated by Ostcn Sacken) this dividing line lies below the 

 middle of height of head and the portion of a single eye below it is 

 broadly sigmoid in outline. 



Indications of intergrading occur, however, in this otherwise 

 satisfactory structural character. The appearance of females 

 collected with males of the two forms certainly suggests that the 

 two will eventually be found to be fully connected by intergrades. 

 The only difference at all apparent between two series of females 

 is the more pronounced whitish appearance of the wing membrane, 

 and less brownish suffusion along costa and veins in sulcifrons 

 (as here separated). 



T. superjumentarius Whitney. Beltsville, McL, June 18 and 

 July 4, 1916, July 10, 1909, McAtee; Chain Bridge, Va., July 19, 

 1916, T. E. Snyder; Falls Church, Va., July 1, 1914, Wm. 

 Middleton. 



T. trimaculatus Palisot de Beauvois. Odenton, Md., July 

 4, 1913, Beltsville, Md., June 18, 1916, July 10, 1909, McAtee; 

 Maryland near Hummers Island, July, 1907, Wm. Palmer; 

 Plummers Island, Md., male, July 2, 1907, H. S. Barber; July 

 21, 1907, A. K. Fisher; Washington, D. C., male June 23, 1898, 

 no collector given; June 24, 1906, McAtee; Great Falls, Va., 

 June 12; Falls Church, Va., June 10 and 24, Nathan Banks. 



T. trispilus Wiedemann. Odenton, Md., July 4, 1913, Mc- 

 Atee; Beltsville, Md., male, June 25, 1915, R. C. Shannon; July 

 4, 1916, Walton, McAtee; July 16, 1916, Walton; Bladensburg, 

 Md., June 23, 1916, R. C. Shannon; Maryland near Plummers 

 Island, July 2, 1916, A. K. Fisher; Virginia near Plummers 

 Island; Md., June 15, 1908, McAtee; Falls Church, Va., male on 

 flowers of chinquaqin June 10, 1913, C. T. Greene; female on 

 flowers of Ceanothus, June 14, Nathan Banks; Glencarlyn, Va., 

 June 26, 1910, male on Ceanothus flowers, F. Knab. 



T. variegatus Fabricius. This species, which is related to 

 abdominalis and sulcifrons, is not well understood and as noted 

 in the discussion of sulcifrons the names for this group are con- 

 fused. A thorough overhauling of this section of the genus is 

 needed. T. variegatus is recorded from the District of Columbia 

 by Osten Sacken. (See Bibliography.) 



' T. vivax Ostcn Sacken. Beltsville, Md., August 8, 1915, Mary- 

 land near Plummers Island, July 2, 1916; Scotts Run, Va., July 

 25, 1915, McAtee; Falls Church, Va.. July 3, 1910, J. N. KnulL 



