100 PROCEEDINGS OF THE NATIONAL MUSEUM vol.90 



Female genitalia. — Ostium spindle-shaped (transverse). Genital 

 plate moderately broad, produced anteriorly, the production of the 

 anterior margin as wide as the genital plate is long. Ductus bursae 

 membranous, variable in length; inception of ductus seminalis just 

 anterior to ostium. Bursa copulatrix not abruptly defined but 

 formed by the gradual broadening of the ductus bursae. Signum a 

 sclerotized, toothed, diamond-shaped plate. 



Alar expanse, 19-24 mm. 



Types. — In the British Museum {argillacea) ; in the United States 

 National Museum {hlacella). 



Type localities. — Newville, Tehama County, Calif, {argillacea) ; 

 Shasta Eetreat and Truckee, Calif, (blacella). 



Food plant. — Salix spp. 



Distribution. — Western United States and western Canada and 

 northeastern United States and eastern Canada. 



United States records 



California: Sacramento, 11 $ $,2 9 9 (V-10 to 24-33, H. H. Keifer [reared]) ; 



Truckee, 8 S $, 8 9 9 (August and October dates, Ximena McGlashan). 

 Idaho: Johnson's Bar, Snake River, 9 (IV-l()-26, J. F. G. Clarke). 

 Oreg-on: Fort Klamath, Fort Watson (Walsingham). 

 Pennsylvania: New Brighton, 9 (VI-20-07, H. D. Merrick). 

 Washington: Dieringer, 9 (VIII-1-32, W. W. Baker [reared]) ; Battleground, 



Clark County, $ (VIII-22-30, J. F. G. Clarke) ; Logan Hill, Chehalis, $, 



9 (II-5-30, III-28-30, T. M. Clarke) ; Pullman (4 $ $, S 9 9, March to 



November dates, T. M. and J. F. G. Clarke [reared]). 



Canadian records 



British Columbia: Duncan, 9 ("1-10-12", Hanham) ; Vancouver, $ (IV-6-03) ; 



Victoria, $, 9 ("7-9-03" ; "3-7-03") ; Wellington, 2 $ $ (IV-30-02), 9 9 



("2-5-02"; "20-4-07") 4 S S (April, G. W. Taylor). 

 New Brunswick: Frederickton, 9 (Aug. 27, 1929, R. P. Gorham). 

 Ontario: Biscotasing, $ (VIII-4-31, Karl Schedl) ; Bobcaygeon, $ (VIII-16-32, 



J. McDunnough) ; Stittsville, $ (21-VIII-1939, E. G. Lester). 



Remarks. — The study of 22 male and female genitalia slides, to- 

 gether with host records, convinces me that the above synonymy is 

 correct. 



A paratype of Walsingham's argillacea is before me. This speci- 

 men, in good condition, although somewhat faded, exactly matches 

 specimens of hlacelln. All the male genitalia are identical except 

 for slight variations in the harpe, a phenomenon frequently encoun- 

 tered in this gi'oup. The female genitalia show wide variation in the 

 length of the ductus bursae, but a study of Busck's cotypes of hlacella 

 show this wide variation in length even in the type series. The length 

 of the ductus bursae is not a reliable character for the separation of 

 species of this group. 



