Syrphidae. 



23 



After the segments not transformed foUow those which are trans- 

 formed and constitute the exterior genitalia ; the number of these 

 segments is, according to the above, four or five, as the last is always 

 the ninth. The exterior genitalia are of a shape characteristic for the 

 faraily; they are unsymmetrical, turned from the left to the right, and 

 they are lying below the apex of abdomen; from above generally 

 only the eighth segment is seen as a smaller or larger knob at the 

 apex (and hence it is in descriptions often termed the fifth or sixth); 

 below generally all the segments may be seen, or only the first of 

 them is hidden under the last not transformed ventral segment (figs. 

 5 and 6). The transformed segments are small, forced over in the 



Fig. 5. Syrphus ribesii. Fig. 6. Pipiza quadriniaculafa. 



Abdomen from the ventral side, shoving the hypopygium. 1 — 8 the eight 

 segments, 9 the hypopygium; in fig. 6 the fifth segment is hidden. 



left side ; the first of them is sometimes present in the whole breadth, 

 but short and more or less unsymmetrical, the others are narrow, 

 only occupying the left side; the tergites are quite hidden under the 

 last normal dorsal segment, and the segments are unsymmetrical in 

 shape; the genital segments curve over towards the right, so that the 

 eighth is lying just at the apex of abdomen, this segment is not 

 divided into tergite and sternite; after the eighth segment foUows the 

 ninth, the real hypopygium, lying in the right side and sometimes 

 partly hidden under the last normal ventral segment; the hypopygium 

 may be of various shape and shorter or longer; it bears at the end 

 below (when in normal position) a pair of claws, very varying in 

 size and shape, symmetricai or unsymmetrical, and from its base 

 above arises a large, very complicated and very variously shaped 



