22 Syrphidae. 



length. Labium highly semitubular; it has the basal part well chiti- 

 nized and of the length of, or shorter or longer than the labella ; these 

 latter are generally oval, sometimes broadly oval or on the contrary 

 long and narrow; they are able to be spread out to a more or less 

 disclform part. The labium has a somewhat long basal connecting 

 membrane. Thorax rectangular or quadrate; pro- and metathorax 

 small; there is no chitinized metasternum behind the hind coxæ, ex- 

 cept in single cases {Sphegina and Neoascia), and also here I think 

 the chitinization is in reality the meeting metaepimera; these latter 

 are characteristic ; they send a process up on each side of the base 

 of abdomen behind the balteres (somewhat recalling the facts in thé 

 Dolichopodids) ; this process stands sometimes out on each side of 

 the base of abdomen as a pointed protuberance f. inst. in Neoascia 

 and Xylota. The first abdominal spiracle is placed quite close to this 

 process and often more or less imbedded in it, so that it may look 

 as if the spiracle was lying in the epimeron. Scutellum is either yellow 

 or yellowish, often translucent, and sometimes partly black, or it is 

 black or æneous, concolorous with the thorax; this colour of the 

 scutellum is of some systematic value; scutellum is either bare below 

 the margin, or it has here a more or less distinct fringe of down- 

 wards directed hairs; in a single genus {Microdon) it has two small 

 marginal spines or processes, in other cases the margin is serrated 

 (Eumerus). Metapleura (Osten Sacken) densely clothed with short 

 hairs, sometimes a little longer towards the hind margin, There are 

 generally no thoracai or scutellar bristles; such are only present in 

 few cases {Chilosia, Vollucellinae, Ferdinandea), and are then noto- 

 pleural, supraalar and postalar bristles and scutellar marginal bristles ; 

 generally also mesopleural bristles are then present, and sometimes 

 a row in front of scutellum; in Ferdinandea there are also post- 

 humeral bristles. Abdomen rather varying in shape; in most cases 

 it is elongated oval or more parallel sided, but it may vary from 

 rather short ovate to very long and narrow, and in the latter case it 

 is generally more or less constricted about the base and club-shaped. 

 The first segment is small or somewhat small. The number of not 

 transformed segments is somewhat varying, and is to some degree 

 characteristic for the groups. In the males the number of dorsal 

 segments varies from four to five; the last is often small, but some- 

 times as large as the others; the number of not transformed ventral 

 segments is generally the same as for the dorsal, but in some cases 

 {Paragus, Chrysotoxum) there is one ventral segment less than there 

 are dorsal, and sometimes the last ventral segment is small and more 

 or less hidden under the genitalia even if not really transformed. 



