Key to Cerodontha , 1. Frons strongly projecting above eye (fig. 572) 2 
Subgenus Butomomyza — Frons not projecting above eye 3 
Species 2 (1). Mesonotum black £. (15. ) gibbardi Spencer 
Synopsis. Head (fig. 572) with frons and orbit 
black; lunule distinctly higher than a semicircle; 
3d antennal segment small, round in both sexes; 
mesonotum black, with 3+1 strong dc ; acr in 4 rows, 
prsc present but irregular; pleura black but upper 
margin of mesopleuron narrowly bright yellow; legs 
black, even foreknee not noticeably pale; squama, 
fringe, and wing base bright yellow; wing length 
2. 4-2. 8 mm, last and penultimate sections of vein 
M 3+4 equal; male genitalia with aedeagus (fig. 
573) having characteristic curvature, distal tubules 
diverging at angle of 90°. 
Host/Early Stages. Unknown. 
Distribution. California, Idaho; Canada. 
References. Spencer, 1969a: 119; 1981: 188. 
— Mesonotum gray U. (E>. ) parvella Spencer, n. sp. 
Synopsis. Agreeing closely with C. gibbardi but sub- 
stantially smaller, wing length in male 2 mm; en- 
tirely black legs are important character; male 
genitalia with aedeagus (fig. 574) having distal 
tubules short. 
Host/Early Stages. Unknown. 
Distribution. Colorado. 
Reference. Part 2, p. 281. 
3 (1). Squamal margin and fringe dark, brownish black 4 
— Squamal margin and fringe pale, yellowish 5 
4 (3). Male genitalia with aedeagus short, distal tubules 
greatly enlarged at end (fig. 575) 
C. (B. ) scirpi (Karl) 
Synopsis. Orbit with 2 ors , lower directed upward 
and slightly inward, 2-4 strong ori; lunule higher 
than a semicircle, almost U-shaped; 3d antennal 
segment small in both sexes, arista long, equal to 
height of eye; mesonotum black, prsc normally well 
developed but variable; legs black, only foreknee 
yellow; squama gray, fringe brownish to black; wing 
length 2. 2-2.8 mm; male genitalia with aedeagus 
having distinctive curvature, distal tubules greatly 
enlarged at end (figs. 575, 576). 
Host/Early Stages. Scirpus spp. (in Europe mainly 
j5. sylvaticus ) . Larva forming very long narrow mine 
running down leaf and into leaf sheath, where pupa- 
tion takes place; puparium yellowish to reddish 
brown, posterior spiracles each with 3 fingerlike 
bulbs arising from conical projection. 
Distribution. California; Canada, widespread in 
Europe . 
References. Spencer, 1969a: 123; 1981: 189. 
Male genitalia with aedeagus having long distal 
tubules, almost vertical to mesophallus with only 
slight curvature at end (fig. 577) 
C. (j5. ) fusculata Spencer, n. sp. 
Synopsis. Closely resembling both £. scirpi and C. 
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