208 THE CANADIAN ENTOMOLOGIST 



being about one and one-half times the length of the halteres; 

 in aspidoptera (fig. 9) the wings are short and broad, and extend 

 to about two-thirds the length of the halteres. 



Limnophila (Prionolabis) cressoni,sp. n. 



Dark brown with the thoracic stripes indistinct; wings with 

 narrow, grayish brown seams to the cross-veins and deflections 

 of veins. 



Male. — Length 8 mm.; wing 10.6 mm. 



Female. — Length 10 mm.; wing 10.8 mm. 



Rostrum short, dark brown; palpi dark brown. Antennae 

 short, dark brown; the flagellar segments very short, almost 

 rounded, with an abundant white pubescence. Head gray. 



Thoracic dorsum dark brown with a sparse, yellowish gray 

 bloom, the praescutal stripes poorly defined. Pleura clearer gray, 

 the dorsal-pleural membranes brownish. Halteres dull yellow, 

 the knobs a little darker. Legs with the coxse and trochanters 

 dull brownish yellow, darkened toward their apices, this dark tip 

 broadest on the fore and middle femora, narrowest on the hind 

 femora; tibiae brown, the tips narrowly dark brown; tarsi brown. 

 Wings with a pale, brown suffusion; stigma dark brown; broad, 

 grayish brown seams along the cord, the outer end of cell 1st Mi 

 and at the origin of the sector. Venation (fig. 7) •i?2+3 about as 

 long as the basal deflection of Cu\. 



Abdomen brown, the terminal segments darker. Hypopygium 

 of the male with the ninth tergite having a broad, V-shaped median 

 notch that is bordered Avith pale reddish brown; ventral pleural 

 appendage with a few scattered teeth that are not prominent. 



Female quite similar to the male, the ovipositor with elon- 

 gate, acute, nearly straight tergal valves; sternal valves elongate, 

 only a little shorter than the tergal pair. 



Holotype, cf, Lagunitas Canyon, Marin Co., California, March 

 29, 1908, (E. T. Cresson, Jr.). 



AUotopotype, 9 . 



The types are in the collection of the American Entomological 

 Society, Philadelphia. 



This fly differs from the only described regional member of 



