476 



Wirth and Stone: Diptera 



prescutellar acrostichals absent; postocellars weak or 



absent 2 



2. Face with 4 pairs of strong, equally developed bristles 



in line; scutellum with discal setulae 



Canaceoides Cresson 



— Face with 3 pairs of strong bristles and 1 or more fine 

 setulae below and between these; scutellum without 

 discal setulae Nocticanace Malloch 



California Species of Canaceidae 

 Genus Canace Haliday 

 aldrichi Cresson 1936. 



Palo Alto, on 

 San Francisco Bay 



Genus Canaceoides Cresson 

 nudata (Cresson) 1926. California seacoasts 



Genus Nocticanace Malloch 



arnaudi Wirth 1954. 



Marin to Orange counties 



REFERENCES 



WHEELER, M. R. 



1952. The dipterous family Canaceidae in the United 

 States. Ent. News, 63:89-94. 

 WILLIAMS, F. X. 



1938. Biological studies in water-loving insects. Part 

 III. Diptera or flies. A. Ephydridae and Anthomyiidae. 

 Proc. Hawaii. Ent. Soc, 10:85-119. 

 WIRTH, W. W. 



1951. A revision of the dipterous family Canaceidae. 



Occ. Paps. B. P. Bishop Mus., 20:245-275. 

 1954. A new intertidal fly from California, with notes on 

 the genus Nocticanace Malloch (Diptera; Canaceidae). 

 Pan-Pac. Ent., 30:59-62. 



Family SCIOMYZIDAE (= TETANOCERIDAE) 



Adult "marsh flies" are frequenters of stream banks, 

 pond shores, and marshy swales. They are easily 

 recognized by their characteristic head shape with 

 porrect antennae and bright colors, often with pictured 

 wings. The known larvae (fig. 14:61c, c) are slender 

 and more or less cylindrical, tapering toward the 

 ends; the posterior end has a short, tapered air tube 

 bearing the posterior spiracles surrounded by a num- 

 ber of oval or triangular lobes. The body segments 

 are each provided with a ring of short rounded warts 

 or tubercles. Anterior respiratory organs are small 

 and retractile, with few branches; the posterior spir- 

 acles each have three spiracular openings and are 

 usually provided with four palmate tufts of float hairs 

 (fig. 14:616). The puparia are yellowish to brownish, 

 short oval, and usually curved upward at one or both 

 ends, with the caudal lobes of the larva much shrunken 

 in the puparium. 



Berg (1953) recently presented convincing evidence 

 that the larvae of Sciomyzidae feed only as predators 

 on snails. Larvae of ten genera have been reared from 



Fig. 14:61. Sciomyzidae. a, Di'cfyo, larva, lateral view; b,c, 

 Sepedon, larva: b, caudal view of spiracular plate; c, lateral view 

 of larva (Peterson, 1951). 



snails, mostly aquatic species. The puparia found 

 in these snails show extraordinary adaptation in form 

 to fit the curvature of the host shell. Cresson (1920) 

 and Melander (1920) have presented concurrent revi- 

 sions of the American species of the family; the 

 following keys are taken largely from the latter. The 

 family is presently being studied intensively by 

 Steyskal (taxonomy) and Berg (biology). 



Keys to the North American Genera of Sciomyzidae 

 Adults 



1. Propleural bristle present; 2nd antennal segment short 

 (SCIOMYZINAE) 2 



— Propleural bristle absent; 2nd antennal segment elon- 

 gate (TETANOCERINAE) 5 



2. Anterior tibia with 2 approximate preapical bristles 

 dorsally 3 



— Anterior tibia with 1 dorsal preapical bristle 4 



3. Arista densely short white haired; not California 

 Oidematops Cresson 



— Arista with long, black rays; not California 



Sciomyza Fallen 



4. Front polished black; cheeks narrow; not California 

 Pteromicra Lioy 



— Front dull; cheeks moderately broad 



P herb ellia Robineau-Desvoidy 



5. Scutellum with 1 pair of bristles 6 



— Scutellum with 2 pairs of bristles 7 



6. Second antennal segment longer than the 3rd 



Sepedon Latreille 



— Second antennal segment shorter than the 3rd; not 

 California Hemitelopteryx Cresson 



7. Third antennal segment oval, 3 times as long as the 

 2nd; front distinctly narrowed anteriorly 8 



— Third antennal segment rarely oval, usually flattened 

 or concave above, the 2nd segment at least 1/2 as 

 long as the 3rd; sides of front nearly parallel 9 



