72 c Canadian Arctic Expedition, 1913-18 



Hylemyia Robineau-Desvoidy. • 



This genus is not well defined, and it is very difficult, in fact almost im- 

 possible, to separate some species from the genus Phorbia by the application of 

 characters given in published keys to the genera of the family. 



The larvae are very little known; those that are known live either in decaying 

 vegetation or, rarely, in living plants such as wheat. 



Hylemyia variata (Fallen.) 

 Musca variata Fallen. Dipt. Suec, Muse, p. 59, 1820. 



There is one female of this species in the collection, taken at Nome, Alaska, 

 August 24 and 25th, 1916 (F. Johansen). 



There are records of this European species from many states in North 

 America, its range extending from Massachusetts to Idaho, and south to 

 Louisiana. It has also been recorded from Ontario and Alaska, so that in all 

 probability it is to be found throughout the entire area of North America. 



Hylemyia acrostichalis, n. sp. 



Male. — Black, shining. Wings clear. Calyptra white. Halteres yellow. 



Eyes separated by not more than width of anterior ocellus; frons not 

 buccate; antenna? nearly as long as face, third joint narrow, about twice as long 

 as second; arista with short, rather dense hairs, the longest hairs longer than 

 diameter of arista at base; cheek not much higher than width of facial orbit in 

 profile, and about one-seventh as high as eye, bristles confined to margin, one 

 short bristle above vibrissa; proboscis not very stout. Prealar bristle long and 

 strong; two pairs of long presutural acrostichals present. Abdomen in type 

 crushed; fifth sternite with a deep central excision, the lateral extensions with a 

 fringe of front hairs on inner margin, and a number of bristles on surface, the 

 longest of which does not exceed in length the lateral extension (PI. X, fig. 39); 

 hypopygium small (PI. X, fig. 40). Legs slender; fore tibia with one posterior 

 and a weaker antero-dorsal bristle near middle, and a small sharp bristle at apex 

 on posterior side which is directed downward and slightly backward; fore tarsi 

 slender, longer than tibia; mid femur with five to six bristles on basal half of 

 postero-ventral surface; mid tibia with one to two bristles on each of the following 

 surfaces: — antero-dorsal, postero-dorsal, and postero-ventral; mid tarsus normal, 

 not longer than tibia; hind femur with long widely-spaced bristles on antero- and 

 postero-ventral surfaces, those on the latter weaker and not carried to apex; hind 

 tibia with three to four bristles on each of the following surfaces — antero-ventral, 

 antero-dorsal, and postero-dorsal, those on the latter surface much stronger 

 than the others, especially the one nearest apex, posterior surface with one 

 bristle near middle; hind tarsus normal, shorter than tibia. Costa with weak 

 setulae, the costal thorn distinct but not very long; last section of fourth vein 

 1 • 75 times as long as preceding section. 



Female. — Similar to male in colour. 



Frons nearly one-half the head-width; cruciate bristles long; each orbit 

 with one strong bristle below the forwardly directed supraorbital; cheek narrower 

 than in male. Thorax as in male, the bristles stronger. Genital segments not 

 armed with strong spines. Legs similar in armature to those of male. Costal 

 thorn longer than in male, the upper exceeding the inner cross- vein in length; 

 last section of fourth vein very little longer than preceding section. 



Length, 6-5 mm. 



Type locality: Nome, Alaska, August 21, 1916 (F. Johansen). 



This species bears a resemblance to marginata Stein, but differs in armature 

 of fifth abdominal sternite, almost contiguous eyes, and armature of legs. From 

 simpla Coquillett, an Alaskan species, it is readily separated by the bristling of 

 the hind tibia. 



