Tachinidae. 45 



in a membrane which is present along each side, and the tergites are 

 less bending in; in other groups the tergites bend more inwards, 

 and no membrane is visible, but the sternites are all visible, and 

 especially the second is seen either lying distinctly on the lateral 

 margins of the tergite or lying between these margins; fmally the 

 tergites may be bending quite in, covering the sternites more or 

 less, often meeting in the middle so that all sternites are quite con- 

 cealed. When abdomen of the male is seen from above, generally 

 only four segments are counted anterior to the two last or genital 

 segments; in some Phasiinae there may, however, be seen five, and 

 also f. inst. in Ernestia five may be seen, the apical of them more or 

 less hidden. The real number of segments is, of course, another. 

 On the ventral side there are five distinct sternites; the lirst of them, 

 lying quite at the base, seems to have no tergite; if abdomen is 

 prepared ofT, there are, however, seen two small more or less ven- 

 trally lying piates, each with a spiracle; these are the rudimentary 

 first tergite (the facts are generally about as shown by Parker for 

 Ravinia: Proceed. Boston Soc. Nat. Hist. 35, 1914, PL V, fig. 30); 

 sometimes the piates seem to be really united with the second tergite, 

 but there are then two spiracles on each side, showing that there 

 are two segments. The first distinct tergite is thus the second and 

 then follow the third, fourth and fifth. Behind the fifth there may, 

 as said, sometimes be seen a narrow sixth, more or less hidden, but 

 by preparation the sixth may generally or always be shown. When 

 it is quite hidden it is generally quite rudimentary; it lies in the 

 membrane above as a small arch {Sarcophaga), often divided in the 

 middle, and it bears bristles, and on each side there is a spiracle 

 either lying in the arch or in the membrane near it; from the left 

 side of the arch a narrow chitinous stripe is seen, going downwards 

 and forwards under the fifth sternite and bending up, but then 

 abrupted and not reaching up on the right side. This dorsal and 

 ventral arch thus represent the sixth segment. Then follow the 

 two genital segments the sternites of which cannot be made surely 

 out, though a sternite to the hypopygium seems to be present. At 

 the apex of the hypopygium there is a membrane with the anal 

 opening, often with a pair of small lips, representing the last segment. 

 After the foregoing we would thus come to a number of nine seg- 

 ments in all, the said rudimentary end segment included. Now the 

 hypopygium no doubt represents in reality the ninth segment, and 

 if so, a segment must have disappeared. I think it is the seventh 



