Syrphidae. 27 



and the alula large, more or less tongue-shaped^ but in some genera 

 both lobe and alula are small or almost wanting, The wing-membrane 

 is nearly always microscopically hairy, only in Eristalis it is bare, as 

 already noted by Meigen. The squamulæ are of a shape characteristic 

 for the family; they are both developed, generally large, sometimes 

 smaller; they may be of equal size or unequal ; at the angulus they 

 are somewhat bladdery; the thoracai squamulæ have a fringe of 

 generally long to very long hairs which are more or less richly 

 branched or furcately divided ; the alar squamulæ are likewise fringed, 

 but the hairs are generally shorter, sometimes quite short, they are 

 sometimes simple but most often they are curiously flattened; the 

 squamulæ are short-haired on the surfaces, but in some cases they 

 have long hairs on at all events a part of the surface, The upper 

 edge of the pteropleura below the vving-root is prolonged backwards 

 into a shorter or longer, thread-like filament, the plumula; it is more 

 or less long-haired with plumose or simple hairs; in a few cases it 

 is rudimentary or wanting; this organ is otherwise characteristic for 

 the family (though indications of a similar prolongation are found in 

 some Dolichopodids [Neurigona] and Empidids). The wings are in 

 rest borne parallel over the abdomen, one covering the other, or they 

 are held more or less open ; for the various genera a various way of 

 bearing the wings at rest has been stated, but this is, I think, not 

 possible ; as far as I have observed all (or nearly all) genera are able 

 to close the wings over abdomen, some do always so at rest, while 

 others often hold the wings half spread but also sometimes close them. 

 As seen the venation of the wings is rather uniform, and it is 

 rather like the common Muscid-type, but differs by the invariably 

 closed first posterior cell and the long anal cell, the vena spuria and 

 other characters. In spite of the uniformity of the venation it ex- 

 hibits many characters of value in its special formation, thus by the 

 place of the medial cross-vein, the straight or more or less curved or 

 looped course of the cubital vein, the open or closed subcostal cell, 

 the marginal cross-veins lying near the margin and parallel with it or 

 more retracted and perpendicular or recurrent with the lower corners 

 angular or rounded and the upper angles acute or rectangular, the 

 strength of the vena spuria and finally also the presence or want of 

 alula. Verrall thinks the bristles on the basal part of the radial vein 

 characteristic for certain groups, but as said above these bristles are 

 nearly always present. Girschner has in his beautiful work (111. 

 Zeitschr. fiir Entom. 1897, 534) given many characters, especially from 

 the squamulæ and the wings, but it seems to me, that many of them 

 are, to be sure, of great interest but however not of the importance 



