6 Orthorrhapha brachycera. 



On the pteropleura, below the squamula, there is generally or always 

 a more or less distinct, flat, somewhat membranous process. Scutellum 

 bare or more or less pubescent or hairy above, often especially at 

 the margin; it has generally two marginal bristles, and as a rule at 

 each side a small hair; sometimes there are also small hairs between 

 the marginal bristles; scutellum may sometimes have four marginal 

 bristles, rarely six. Abdomen longer or shorter, sometimes even 

 shorter than thorax (f. inst. Ht/drophorus) ; it is usually more or less 

 narrowed towards the end and thus somewhat conical; but when it 

 is specially long, it is generally thin and slender, and not or slightly 

 narrowed towards behind. It is cylindrical, often a little compressed, 

 sometimes more compressed, or on the contrary flattened. In the 

 female it is generally more or less pointed. The dorsal segments of 

 abdomen are much broader than the ventral, and arched; the ventral 

 segments are more narrow and flat; thus the dorsum and the sides 

 are formed of the dorsal segments, The first dorsal segment is gener- 

 ally shorter than the following, at other times of the same length or 

 even longer; it is rarely a little broader than the second; the first 

 ventral segment is very short, only forming a small chitinisation just 

 in front of the second; sometimes it is perhaps not at all chitinised. 

 In the male the abdomen has eight segments, then follows the hypo- 

 pygium, formed of the ninth segment, Sometimes all eight segments 

 are visible, those in front of the hypopygium more or less decreasing 

 in size, but often some of the latter are more or less hidden, so that 

 only five or six segments are visible anterior to the hypopygium. 

 More or fewer of the anterior ventral segments are normally developed, 

 the following more or less incised, with membranous parts or quite 

 membranous. These latter are folded up groove-like, so that a smaller 

 or larger cavity for the reception of the hypopygium is formed, The 

 seventh segment is small and generally unsymmetrical; it has a chiti- 

 nised sternite, generally lying at the ventral base of the hypopygium, 

 but sometimes in front of it, The eighth segment is always of a 

 curious shape, peculiar to the family; it is scale-like, of various circum- 

 ference but often roundish; it is not divided into tergite and sternite, 

 and it lies always on the left side of the hypopygium; its anterior 

 opening lies at the anterior end, and its posterior opening on the in- 

 side, and the two openings are on the inside only separated by a 

 rather narrow bridge. The ninth segment or the hypopygium seems 

 to be of the same principal structure throughout the family, but may 

 otherwiso vary considerably in shape; it is smaller or larger, generally 

 somewhat oval, and more or less elongated, or short and roundish; 

 it is often more or less compressed. The cavity of the eighth segment 



