OCHTHERA. 



249 



group, unless it be with certain species of the Geomyzida, which 

 appear to offer the nearest affinity. Nevertheless from these the 

 Hydromyzida may be distinguished either by the form of the head 

 and mouth, the characteristic imperfection of the areolets of the 

 wing, or the total concealment of the ovipositor. The greater 

 number frequent the neighbourhood of waters, a destination indi- 

 cated by the satiny lustre of the minute scales which clothe the 

 face and sides. Ephydra riparia, the feet of which are formed 

 peculiarly for resting on the surface of pools, is here regarded as 

 the type of the group. The larvse of most Ephydra live among 

 the semi-fluid green matter which mantles on the surface of stag- 

 nant waters, or in the mud at the bottom. Desvoidy assumes 

 that the other genera of the tribe, in their larva state, are nourished 

 by the living tissue of phanerogamous plants ; but this view rests 

 on conjecture, and a solitary fact observed regarding a species of 

 Notiphila. The form and homogeneous texture of the face in- 

 dicates but little sensibility to smells, from whence we may pro- 

 bably conclude that the larvae are not eminently saprophagous." 

 Haliday. 



SYNOPSIS OF THE GENERA, 

 /'oval, incrassated 1. OCHTHERA. 



Fore femora 



f densely pilose 3. HYDEELLIA. 



.like the pos- \ 



terior. Eyes j bare, or with scattered f unguiculate 2. NOTIPHILA. 

 C hairs. Second joint- < 



of the antennae . (. not ungui- 

 culate . 4. EPHYDRA. 



Genus I. OCHTHERA. 



OCHTHERA, Latr. H. N. xiv. 321 (1814 ?) ; Pal.; Meig. ; Mcq. ; Desv.; 

 Hal. ; Zett. Musca p., D. G. ; F. Tephritis p., F. 



Corpus vix nisi nudum. Caput subtus attenuatum, subtrigonum. 



Vertex impressus. Clypeus exsertus, suborbiculatus. Oculi magni, 



protuberantes. Palpi exserti, dilatati. Arista dorso ciliis perpaucis 



pectinata. Yena discali-recurrens obliquata. Areola priraa exterior 



apice attenuata. Abdomen deplanatum. Pedes antici femoribus 



crassis ovatis, tibiis arcuatis acutis. Metatarsus posticus incrassatus. 



Body almost bare. Head nearly triangular, attenuated beneath. 



Vertex impressed. Clypeus projecting, suborbiculate. Eyes large, 



prominent. Palpi exserted, dilated. Arista with very few bristles 



above. Discal-recurrent vein oblique. First, exterior areolet attenuated 



VOL. ir. 2 K 



