182 Proceedings of the Biological Society of Washington. 



28, 1916, H. L. Viereck; Cabin John. Md., June 14, 1913; Great Falla, 

 Va., April 20, 1913; April 22, 1915, Shannon, April 20, 1913, F. Knab; 

 May 2, 1916, McAtee; Washington, D. C, April 30, 1915, G. E.Quinter; 

 Rosslyn, Va., May 1, 1913, Shannon; Falls Church, Va., April 28,1913, 

 Greene; June 16 and July 7, Banks; Four-mile Run, Va., April 25, 1915. 



M. OBSCURUM Say. — Very common; on many kinds of flowers; April 

 10 to October 26. 



Didea Macquart. 



D. FAsciATA Macquart. — Plummers Id., Md., June 11 and 20, 1912; 

 June 1, 1913, in wasp's burrow, H. S. Barber; October 7, 1906, A. K. 

 Fisher; Washington, D. C, June 6, 1912, McAtee; Chain Bridge, D. C, 

 September 15, 1912, F. Knab and J. R. Malloch; Hyattsville, Md.,May 

 13, 1913, A. Busck; Lanham, Md., May 3, 1915, F. H. Loomis; Somer- 

 set Heights, Md., July 11, 1903, E. S. G. Titus; Washington, D. C, 

 September 20; Falls Church, Va.,July; Banks; Veitch, Va., September 

 23, 1913, Greene. Generally on foliage in sunny places ; larvae attack 

 aphids. 



Syrphus Fabricius. 



S. AMERiCANUs Wiedemann. — Everywhere, occurring continuously 

 throughout the season; extreme dates are April 8 to November 2. 



S. ARCUATus Fallen.— Falls Church, Va., April 22, and May 26 to 30, 

 1913, Greene; May 4 and 25, Banks; Great Falls, Va., April 19, 1915, 

 Greene; Glencarlyn, Va., June 14, Banks; Washington, D. C, May 16, 

 1913; May 29, 1913; College Park, Md., May 25, 1913, F. Knab; Belts- 

 ville, Md., May 2, 1915, L. 0. Jackson; Hyattsville, Md., July 9, 1909, 

 pupa collected on leaf, fly emerged later, McAtee; Plummers Id., Md., 

 October 7, 1906, A. K. Fisher; Maryland near Plummers Id., April 15, 

 1915, McAtee. Usually near pine trees, aa also S. perplexus ; larva feeds 

 on aphids on pine twigs. 



S. FisHERi Walton. — Glencarlyn, Va., July 14, Banks. 



S. KNABi Shannon.*— Falls Church, Va., June 22, 1912, Greene; June 

 21, 1914, F. Knab; July 4, August 30 and September 13, Banks; Glen- 

 carlyn, Va., June 24, Great Falls, Va., June 25, Dead Run, Va., June 

 23, Banks; August 3, 1915, Difficult Run, Va., July 7, 1915, Shannon; 

 Virginia near Plummers Id., Md., April 28, 1907, Beltsville, Md., June 

 18, 1916, McAtee; Lanham, Md., May 3, 1915, F. H. Loomis; Plum- 

 mers Id., Md., June 7 and 28, 1914, June 14, 1908, McAtee; June 1, 

 1913, stored by wasp in its burrow in a log, June 20, 1912, June 30, 

 August 6, H. S. Barber; June 19 and 30, July 19, August 6, Shannon; 

 August 11 and 24, 1907, A. K. Fisher; September 5, 1915, McAtee; 

 Maryland near Plummers Id. , June 18, 1916, L. 0. Jackson ; Cabin John 

 Bridge, Md., July 29, 1916, McAtee; Washington, D. C, September 30, 



* For a key to the section of Syrphus containing this species and descriptions of 

 S. knabi, S. nbesii vittafrons and notes on S. rectus, see Appendix, pp. 199-202. 



