FAMILY EPHYDRID.T: THE SHORE FLIES 347 



leaves. Some of the species are able to walk on the surface of water 

 and many of them will alight upon it if disturbed but they usually 

 quickly return to the shore. 



The larvae live in various habitats, many are aquatic or live in mud, 

 others in the stems of aquatic or semi-aquatic plants, a few in flowing- 

 sap. ]\Iany of them live in l)rackish, but may also occur in fresh, or 

 even in alkaline water. One species, PsiJopa petrolci Coquillett, occurs 

 in the pools of crude petroleum found in California, breathing by pro- 

 jecting the posterior spiracles above the surface of tlic oil, but its food 

 is unknown. Other species are found in the warm waters of geysers. 



IMany new genera have been described since the publication of 

 AVilliston's IManual and some authors have recognized the NotiphilidsB 

 as a separate family but there a])pcars to be no good basis for this. 

 Jones* reviewed the family in 1906. Since then there has been no 

 comprehensive publication although Cresson has published several large 

 papers containing descriptions of new species and genera and some 

 keys. 



KEY TO GENERA. 



1. Scutellum normal 2 



Scutellum as large as the mesonotum and almost concealing the ab- 

 domen, from dorsal view (see text figure) Peltopsilopa Hendel 



2. Costa extending to the fourth vein 3 



Costa ending at the third vein 53 



3. Antennae small, inserted very far apart in cavities, the arista atrophied, 



very short and blunt (7, 8, 71) Lipochaeta Coquillett 



Antennae normal; arista always long 4 



4. Middle tibise with dorsal bristles (30, 57) tParalimna Loew 



Middle tibiae without bristles except at the apex 5 



5. Second antennal segment with a spinous bristle at the upper apical 



corner 6 



Second antennal segment without such bristle 31 



6. First and fifth abdominal segments exceptionally short, the abdomen 



apparently composed of three long segments, the lateral margins 



revolute 7 



Abdomen with five distinct segments, the lateral margins not margined . 8 



7. Face with two pairs of bri?tles below Trimerinoides Cresson 



Face with one pair of bristles below (48) Trimerina Macquart 



8. Arista pectinate 9 



Arista bare (40, 53) Mosillus Latreille 



* Tech. Bull. Calif. Exp. Sta., i. No. 2. 



t Cresson, 191S. Trans-Amer. Ent. Soc, .xliv, p. 45 (Costa Rica). 



