VOL. 54, NO. 1, JANUARY 1978 
37 
not evident; occiput sparsely setose, microtrichiose. Eyes with setae and microtrichia 
between well-separated facets. Anterior spiracular plate as high as long, triangular; no 
supraalar setae; no preepisternal setae; anepisternal setae numerous on anterior margin; 
upper episternal setae 6; subalars 12, subspiraculars 11; lower epimerals 10. Wings 2.65 
mm long, faintly brownish, veins obvious, membrane microtrichiose, costa and radial 
complex with setae; 2nd section of costal margin subequal to section 3; M 2 subequal to 
base M. Abdomen with terga and sterna sparsely setose, densely microtrichiose; 
segments 1-6 unmodified; tergum 7 (Fig. 12) reduced laterally, trilobed on posterior 
margin; sternum (Fig. 12) expanded dorsally to include 7th spiracle; genital vesica and 
apodemes 0.33 mm long. Genitalia (Fig. 13) with tergum 9 produced posteriorly, terminat¬ 
ing in 2 divergent points; gonocoxite setose, emarginate distally; penis valves swollen 
basally, acute apically; penis somewhat sinuous, not projecting beyond gonocoxites. 
Segment 7 very similar to those of European species C. triste (Zetterstedt) and C. 
nigripenne (Meigen) with spiracles in sternum rather than tergum as other North American 
Colobostema. 
Holotype d. Mill Valley, Marin Co. California, 10-IV-40, (H.B. Leech) collector. In 
collection of California Academy of Sciences. 
This species differs from the other American Colobostema with 
unbanded legs in having a truncate median lobe on the posterior 
margin of tergum 7 rather than a median incision. 
Literature Cited 
Cook, E.F. 1956. A contribution toward a monograph of the Scatopsidae (Diptera). Part 
III. The genus Rhexoza. Ann. Entomol. Soc. Amer. 49:1-12 
Cook, E.F. 1958. A contribution toward a monograph of the Scatopsidae (Diptera). Part 
VII. The Genus Psectrosciara Kieffer. Ann. Entomol. Soc. Amer. 51:587-595. 
Cook, E.F. 1975. A Reconsideration of Nearctic Rhexoza (Diptera: Scatopsidae). Pan- 
Pacific Entomol. 51:62-75. 
