FAMILY IMYDAID.K — THE MVDAS FLIES 165 



KEY TO GENERA 



1. Posterior tibise ending in a spur (5, 8) 2 



Posterior tibiae without spur (6) 5 



2. Spur of the posterior tibise longer than the width of the first tarsal 



segment, giving the tibiae an arcuate appearance, the terminal bristle 

 shorter than the spur; antennas (always?) similar in both sexes.... 3 

 Spur small and straight, shorter than the tarsal thickness or the ter- 

 minal bristle; antenna? differing in the two sexes; palpi absent 

 (1, 2, 3, 5. 7) Phyllomydas Bigot 



3. Palpi wholly absent or represented by a bulbous swelling (8. 10; see 



colored plate) Mydas Fabricius 



Palpi well developed, slender and sometimes half as long as the 

 proboscis 4 



4. Posterior femora rather strongly swollen; posterior trochanters with- 



out bristles (13) *Lampromydas Seguy 



Posterior femora not swollen; posterior trochanters bearing short, 

 stout bristles (4, 12) tOpomydas, n. g. 



5. No vein reaching the posterior border between the anal cell and tip 



of the Vv'ing 6 



A vein (the fifth) extends to the wing margin (4, 12). . . .tOpomydas, n. g. 



6. Proboscis extending well beyond the oral opening (6, 11). 



JNomoneura Bezzi 

 Proboscis small, not extending beyond the oral opening (9). 



tNemomydas, n. g. 



* Lampromydas was based on sjieciniens in which there if no vein extendinp to the 

 wing margin oetween the anal vein and the tip of the wing but the character is not generic in 

 this case. Of two specimens of (Mydas) luteipennis Loew. one has a vein in one wing while 

 the other specimen has none. This species and maculivcntris Westwood, as well as two un- 

 identified species before me, belong to Lampromydas unless the genotype of Lampromydas 

 lacks palpi. 



T Ectyphus Gerst»cker is not known from North America but apparently occurs in South 

 America. The three described North American species belong to Opomydas of which E. limbatus 

 Williston is the genotype. 



J Leptomydas Gerstsecker is not known from America. The genus is distinguished by the 

 hairy pleura, both the above genera having pile only on the pteropleura and supraspiracular 

 convexities. The genotype of Nemomydas is Leptomydas pantherinns Gerstaecker. 



Mydaidje.— 1. Phyllomydas phyllocerus, $ ; 2, Phyllomydas phyllocerus, S genitalia from 

 below; 3, Phyllomydas phyllocerus; r" : 4, Opomydas limbatus; ",, Phyllomydas phyllocerus, 

 hind leg: 6. Nomoneura, hind leg: 7, Phyllomydas phyllocerus; N, Mydas clavatus, hind leg; 

 9, Nemomydas panthcrimus ; Ui, Mydas cl.Tvatus ; 11, Nomoneura pananiensis ; 12, Opomydas 

 townsendi, hind leg; 13, Lampromydas maeuliventris. 



