FAMILY TETAXOCERIIXK THE MARSH FLIES 369 



The larvffi are slender, cylindrical, thin anteriorly, the terminal 

 segment with six or eight conical, fleshy tubercles. They are aquatic. 



The North American species have been reviewed by Cresson (1920, 

 Trans. Amer. Ent. Soc, xlvi, pp. 27-89) and JMclander (1920, Ann. 

 Ent. Soc. Amer. xiii, pp. 305-332), the former under the name Sciomy- 

 zidffi. 



KEY TO GENERA 



1. Propleural bristle present 2 



Propleural bristle absent 5 



2. Anterior tibiae with two approximate preapical bristles dorsally .3 



Anterior tibiae with one dorsal preapical bristle 4 



3. Arista densely short white haired (19) Oidematops Cresson 



Arista with long, bla^k rays (20) Sciomyza Fallen 



4. Front polished black; cheeks narrow (21) Pteromicra Lioy 



Front dull; cheeks moderately broad (22) *Melina Desvoidy 



5. Scutellum with two pairs of bristles 7 



Scutellum with one pair of bristles 6 



6. Second antennal segment longer than the third (1, 2, 3, 17, 18). 



Sepedon Latreille 

 Second antennal segment shorter than the third . . . Hemitelopteryx Cresson 



7. Third antennal segment oval, three times as long as the second; front 



distinctly narrowed anteriorly 8 



Third antennal segment rarely oval, usually flattened or concave above, 

 the second segment at least half as long as the third 9 



8. Posterior tibiae with two preapical dorsal bristles (2, 3). 



fRenocera Hendel 

 Posterior tibiae with one preapical dorsal bristle Antichaeta Haliday 



9. Mesopleura and pteropleura with one or more bristles 10 



Mesopleura and pteropleura at most with short hairs 11 



10. One sternopleui'al bristle (12) Hoplodictya Cresson 



No stemopleural bristle (4, 6, 7) jDictya Meigen 



11. Two or three pairs of dorsocentrals 12 



One pair of dorsocentrals (14) Hedroneura Hendel 



12. Two pairs of dorsocentrals 13 



Three pairs of dorsocentrals (25) Poecilographa Melander 



13. Mesopleura and pteropleura bare 14 



Mesopleura and pteropleura with setulae 16 



14. Frontal lunule exposed; wings brown with rounded clear spots 15 



Frontal lunule mostly concealed; wings never with rounded, clear 



spots (5, 24, 26, 27) Tetanocera Dumeril 



Dyctia Desvoidy is an older name but its use conflicts with Dictya Meigen. 

 Cuiran, 1933, Amer. Mus. Novit. No. C.S2, p. 9. 

 Curran, 1932, Amer. Mus. Novit. No. 517. 



