20 DUKHAM DIPTEEA. 



(C.II.6.) A cell is said to be closed when it is not 



bounded at any place by the wing margin. 

 0.2. is open in Plate V.19, closed in Plate V.20. 

 When it is closed some distance from the margin, 

 and one of the enclosing veins continues on alone, 

 it is said to be stalked, as 0.2. in Plate V.20, or 

 0.4 2 in Plate V.24. 



(7) The Stigma. — A thickened portion of the wing at 



the end of V.I. 



(8) The Alula, or Axillary Lobe, O.9. — A rounded pro- 



jection at the hinder base of the wing. 



III. The Halteres. — Knobbed projections behind the 



wings, peculiar to the Diptera and characteristic. 



IV. The Squaivue or Calyptra. — Scale-like appendages 



beneath the wings and above the halteres, generally 

 fringed with hairs. 

 D. THE ABDOMEN.— The hind portion of the body, 

 bearing the organs of generation. 



(1) Segments. — It is divided across into segments in- 



dicated by numbering from the base, that is the part 

 attached to the thorax ; thus, the 1st or basal 

 segment, the 2nd, the 3rd, &c. 



(2) Anus. — The last segment, of a peculiar shape, is 



the anal segment or anus. 



(3) Generative Organs. — From the anus proceed the 



organs of generation. Those of the male are 



called genitalia, hypopygium, or male organs 



(Plate VI. 17). They consist often of a pair of 



forceps (a) springing from the outer upper side 



of the last segment, and a single middle organ 



beneath, the pennis (b). Sometimes a pair of 



plates, often fringed, are present, the lamellce (c). 



The female organ is the ovipositor or vagina, 

 often hidden within the body. 



(4) Plates. — The segments consist of two horny plates, 



the back or upper plate, and the belly or under or 

 ventral plate, united by a more membranous 

 portion, often invisible — the sides. 



