180 Proceedings of the Biological Society of Washington. 



mers Id., Md., flowers of Aruncus, June 2, 1916, McAtee; June 4, 1916, 

 H. L. Viereck; Falls Church, Va., May 30, June 7, 11, and 23, on 

 Ceanothus, and November 6; Glencarlyn, Va., May 30, on flowers of 

 chinquapin. Banks. 



C. PRiMovERis Shannon. — This species described from Plummers Id., 

 Md. , by one of the authors of this Hst is abundant in early spring, March 

 27 to April 27, on flowers of bloodroot, violets, spring beauty and Den- 

 taria. 



C. siMiLis Shannon. — Cabin John, Md., October 30, 1915, Shannon; 

 Virginia near Plummers Id., September 29, 1915, McAtee; Dead Run, 

 Va., October 28, 1915, Shannon; Spring Hill, Va., September 29, 1911, 

 F. Knab; Difficult Run, Va., September 8, 1914, Shannon; Great Falls, 

 Va. , October 3 and 21 , Banks ; October 3, 1915, McAtee ; Glencarlyn, Va. , 

 October 4, on Solidago ; males taken on this date with the females are 

 very dark-winged, Banks. 



Chalcomyia Williston. 



C. AEREA Loew. — Dead Run, Va., May 9, 1916, Shannon ; Falls Church, 

 Va., April 25, on bark of stumps. Banks; May 1, 1913, W. Middleton; 

 May 7, 1915; Great Falls, Va., April 19, 1915, Greene; April 28, 1915, 

 on dead sycamore log, Shannon; Cabin John, Md., April 28, 1915, F. 

 Knab and J. R. Malloch. 



Myiolepta Newman. 



M. NIGRA Loew.* — Falls Church, Va., May 22, 1915, in pocket t at 

 base of tulip tree, Greene; May 30, Banks; Great Falls, Va. , June 21, 

 Glencarlyn, Va., May 30, Banks; Cabin John, Md., May 15, 1904, F. 

 Knab; Beltsville, Md., June 14, 1914, McAtee. 



M. STRiGiLATA Loew. — Falls Church, Va. , April 27 to May 1, 1915, 

 sometimes at base of trees, also on blossoms of Viburnum, Greene; May 

 7 on Viburnum, Banks; Mt. Vernon, Va., on flowers of Amelanchier, 

 May 7, 1916, L. 0. Jackson; Maryland near Plummers Id., May 14, 1915 

 (var. ), Shannon; April 20, 1916, on flowers of Prunus americanus, L. O. 

 Jackson ; Beltsville, Md. , on apple blossoms, April 30, 1916, McAtee. 



M. VARiPES Loew. — Washington, D. C, April 26, F. R. Cole; May 4, 

 1913, May 12, 1914, F. Knab; May 22, W. R. Walton, May 22, 1908, 

 H. O. Marsh; May 25, 1912, McAtee; Bethesda, Md., April 27, 1915, 

 R. H. Hutchinson; Falls Church, Va., April 27, 1915, May 3, 1913, 

 Greene; May 7, 21, and 26, June 28; Chain Bridge, Va., May 21, Banks; 

 Dead Run, Va. , May 21, 1916, Shannon. Captured about bases of trees 

 and on flowers of Viburnum ; larvae in pocket in tulip tree, Greene. 



* For synonymy of Xylota tuberans see Appendix, pp. 198-199. 



t The term pocket as used in this paper means a hollow place or blind hole either in 

 the side or in a crotch of a tree. Such pockets are always filled with dead leaves or 

 other decaying vegetable matter, and keep quite moist from rain water or sap from the 

 tree. 



