REMARKS ON THE GENERIC CHARACTERS. 349 



by the slender structure of the whole body, by the length of their slender 

 feet, by their pedunculated, usually yellow hypopygiuui, which is pro- 

 vided with narrow, linear external appendages and elongated, more or 

 less penicillated, internal appendages, likewise by the always very pro- 

 minent development of the first joint of the arista of the antennae, which 

 is different, however, in different species ; the scutellum is glabrous 

 and the lower part of the female face not protruding. The spocies of 

 Haltericerus are more robust than the species of Hypophyllus ; the face 

 of the male is very narrow, that of the female very broad ; the second 

 joint of the antennae in both sexes, especially in the males, is rudi- 

 mentary, and the arista very elongated in the latter and enlarged at its 

 tip into a lamella ; the hypopygiurn, attached to a long peduncle, and its 

 appendages, bear the greatest resemblance to those of the species of 

 Hypophyllus. 



To the above-named genera of the first group is appended Diostracus 

 (13), as an anomalous genus. The very broad face in both sexes, the 

 palpi, much larger in the male than in the female, the very small third 

 joint of the antennae, the incrassated fore femora, the rounded, but not 

 imbedded hypopygiurn, with its very small appendages and the long nar- 

 row wings, with the posterior transverse vein very close to the margin 

 all these characters render this genus very easy to recognize. 



To the Second Sub-division, which is distinguished by the small, 

 more or less imbedded hypopygium, belong the following genera : Anepsius 

 (14), Argyra (15), and Syntormon (16). In Anepsius the second joint of 

 the antennas has the usual transverse form, and the arista is inserted very 

 close to its basis ; the third joint of the antennae shows a distinct pubes- 

 cence ; the first longitudinal veiu is short, the fourth parallel with the 

 third ; the abdomen of the male is laterally compressed. The relation- 

 ship between Anepsius and the genus Synipycnus, which belongs to the 

 second principal division, cannot be mistaken, though the distinct pubes- 

 cence of the first joint of the antennae distinguishes it very easily from 

 the other. The genus Argyra is distinguished by the transverse form 

 of the second and the rather considerable size of the third joint of the 

 antennae, its subapical arista, the broad wings particularly towards the 

 basis, the length of the first longitudinal vein, its distance from the costa 

 and the inflection of the fourth longitudinal vein ; to these characters 

 may be added, in most of the species, the delicate, but striking silvery 

 white tomentum, spread over a large part of the body. Argyra is closely 

 related to Leucostola, the first joint of the antennae of which, however, is 

 glabrous on the upper side. The genus Syntormon differs from all the 

 other genera of the whole first principal division by the form of the second 

 joint of the antennae, which, on its inner side, overlaps the third joint in 

 the shape of a thumb ; the face of the male is narrow, that of the female 

 broad and protruding below like a roof: the arista of the antennas is com- 

 pletely or almost completely apical; the third longitudinal vein is parallel 

 or almost so. 



