HELEOMYZID FLIES NORTH OF MEXICO—GILL 541 
lected by M. R. Wheeler. This specimen is in the personal collection 
of Dr. Wheeler. 
Genus Anorostoma Loew 
Anorostoma Loew, 1859, p. 47.—Aldrich and Darlington, 1908, p. 75.—Czerny, 
1924, p. 113; 1927a, p. 28; 1935, p. 282.— Curran, 1932, p. 10; 1933, p.1. 
The head in this genus recedes from the lunule toward the oral 
margin. The anterior fronto-orbital bristle is usually about one- 
half the height of the posterior bristle, but the ratio is variable. The 
third antennal segment is oval and the arista microscopically pubes- 
cent. The eye is horizontally oval, usually more so in the male than 
the female. 
The thoracic chaetotaxy is as follows: dorsocentrals 1+3; scutellum 
bare except for 2 pairs of lateral bristles; propleural bristle present; 
mesopleuron with 1 or more bristles along posterior margin, often 
with small hairs above and (or) below the bristle; sternopleuron 
with 1 or more bristles; remainder of pleura bare; prosternal bristles 
absent. 
The middle tibiae have several ventral apical bristles, as well as 
the usual dorsal preapical bristle. 
The color of the wings and abdomen may vary with the species. 
I have examined the types of all species of Anorostoma from North 
America which have been described, except A. raca Garrett. I have 
utilized the male terminalia to a great extent in working out the 
following revision of the genus. Although Garrett’s descriptions 
give no illustrations or detailed accounts of the appearance of the 
male terminalia of his species, his personal notes and drawings, which 
he permitted me to examine, show that he used these structures 
extensively. 
Key to the Species of Anorostoma 
1. Wings with a mottled appearance, contrasting whitish and dark gray areas, 
somewhat opaque. . . 3 2 
Wings hyaline or tinged w th yellowish! prawn or ince bit Hot motéled in 
the form of contrasting whitish and dark gray areas. ........ 4 
2. No black spot from the: base of antenna to eye; cell R, (marginal cell) not 
completely darkened with gray... . . . . cinereum Curran 
A black spot from the base of antenna to eye; cell Ri aoe cell) may or 
may not be completely darkened with gray .. . ea ea 
3. Cell R; completely grayish (in contrast to whitish areas in other parts of 
wing); length of body about 7mm... . . . . opacum Coquillett 
Cell R; not completely stare distal area & cell whitish; length of body 
about 4.5mm ... . . . maculetum Darlington 
4. Mesonotum mottled with many ese cae spats: or if not so, the mesonotum 
is a bluish gray which contrasts with the non-pollinose reddish yellow 
abdomen; sternopleuron usually with 2 or more strong bristles . .. . 5 
