DURHAM DIPTERA. II 



(A. VIII.) (4) The Palpi. — Two feelers attached to the proboscis 

 and often jointed. 

 IX. The Back of the Head or Occiput. — The back 

 edges of the eyes are the posterior orbits, which often 

 bear the post-orbital bristles. 



B. THE THORAX. — The middle portion, bearing the organs 

 of motion. It is divided longitudinally into : — 

 I. The Dorsum, or Thorax. — (The small numbers in 

 brackets refer to the diagram, Plate VI.). 



(1) Boundaries. — It is bounded in front by (a) the 



neck (7), behind by (b) the scutellar suture (15), 

 or seam which separates it from the scutellum (6), 

 a small triangular hump projecting backwards, 

 often bearing several long bristles — the scutellar 

 bristles. At the sides by (c), in front, the dorso- 

 pleural suture (9), a seam running from the front 

 corners of the dorsum to the front of the wing- 

 bases, by (d) the wing- bases (10), and by (<?) the 

 scutellar bridge (11), a ridge running diagonally 

 from the hind base of the wings to the root of 

 the scutellum. 



(2) The dorsum is crossed by a seam — the dorsal 



suture (8). At the front corners is a slightly 

 raised knob — the shoulder or humerus (1). 



Divisions. — In addition to the two shoulders it 

 is divided into six regions by the dorsal suture {%) 

 and a slight ridge, or imaginary line, on each 

 side, running from above the shoulders towards 

 the outer front corners of the scutellum ; namely, 

 two central regions (2, 3), the prce-sutural (2) in 

 front of the dorsal suture, the post-sutural (3) 

 behind it; two post-humeral regions (4), one on 

 either side behind the shoulders, above the dorso- 

 pleural suture and in front of the dorsal suture 3 

 two alar regions (5) above the wings and behind 

 the dorsal suture. 



