1864.] ■ ' 575 



practicable, every four or five weeks by freshly gathered ones; which, 

 as most Willow-galls are exceedingly abundant, is not a matter of much 

 trouble or difficulty. 



In the following Synoptical Tables I have endeavored to separate, by 

 constant and sharply-defined characters, drawn from every available 

 source, the fifteen species of Cecidomyia known by me to form galls on 

 the Willow. After this, each gall and its gall-maker in all its states 

 will be described so fir as known to me, chiefly from recent specimens, 

 and the whole will conclude with descriptions of all the Inquilinous 

 Gnridoiryjidse that are known by me to inhabit any galls of the Wil- 

 low, whether Cecidomyidous or Tenthredinidous, and a list of the galls 

 inhabited by each species, followed by a notice of a few other Diptera 

 that occasionally or habitually breed in Willow-galls. 



SYNOPSIS OF THE CECIDOMYIDOUS GALLS OF THE GENUS SALIX 



(WILLOW). 



A. Gall always monothalamous, and evidently a deformation of a bud. 

 I. Bud with its leaves well develoj)ed. 



T. Galls almost always many of them growing contigu- 1 1, S. brassicoides. 

 ously together, not usually at the tip of a twig. (Gall > n. sp. on S. Ion- 

 large, expanding .73 — 2.25 inch.) J gifolia. 



2. Gall always solitary, and always growing at the tip of a twig, 

 t Leaves of the gall all sessile. 



a. External leaves appressed like the scales of a 

 young pine-cone, and rounded at tip except near 

 the tip of the gall, where they are angulated. 

 (Gall large, expanding .50 — .90 inch.) 



2, S. strobiloides 0. 



S. on S. cordata. 



b. External leaves appressed like the scales of aU s^^^^j^^.j. ,^_ 

 young pine-cone, and a 1 of them angulated at ^^ g_ rostrata. 

 tip. (Gall large, expanding about .(0 inch.) ) '■ 



c. External leaves generally opened out and re- \ 4, S. gnaphalioides 

 curved at tip, and always more or less beaked at > n. sp. on S. hu- 

 tip. (Gall small, expanding .14 — .60 inch.) j mills. 



ff Terminal leaves peduncled, the other external ^ 



leaves sessile and opened out, and at tip recurved I 5, S. rhodoides n. 

 and acutely angulated. (Gall large, expanding [ sp. on S. humilis. 

 .70—1.90 inch.) J 



tfl All the external leaves peduncled more or less. 1 



the terminal ones the most so, and opened out and I g g eoj.YiQ;jgg „ 

 at tip recurved, and obtusely, seldom acutely, an- \ ' ^ ' ^^^ ^ discolor? 

 gulated. (Gall very large, expanding 1.95 — 4.10 -1 • ' • 

 inch.) J 



II. Bud deformed into a long tube: its leaves oblite- ] 7, S. cornu n. sp. on 

 rated. j S. humilis. 



( 



