DURHAM DIPTERA. 9 



(A.III.) (2) The Frontal Orbits. — The sides between the frontal 

 stripe and the eye. 



(3) The Frontal Lunule. — A small crescent-shaped piece 



immediately above the antennas (plate VII. 5), 

 only found in the second sub-order — Cyclorrhapha. 



(4) The Frontal Bristles. — One pair, on the frontal 



stripe, in front of the ocelli. 



(5) The Fronto-orbital Bristles. — A row or rows, on 



either side, on the frontal orbits. They often 

 begin in the vertical portion of the orbit, and 

 extend down towards the cheeks. 



(6) The Loiuer Fronto-orbital Bristles. — On the frontal 



orbit, below the fronto-orbital bristles, but not in 

 the same line. The different rows may be dis- 

 tinguished as inner (nearer to the frontal stripe), 

 outer (nearer to the eyes). 



(7) The Edge or Margin of the Eye. — A narrow, often 



glistening white line on the outer edge of the 



orbits close to the eye. 

 IV. The Antennae. — Jointed processes, springing from 

 the front of the head, often lying close together in a 

 little pit in the middle of the face. The Diptera may 

 be divided into two sections by the number of the 

 joints of the antennae. In the one, the Nematocera, the 

 joints are very numerous (Plate II). They consist of: — 



(1) The Basal joints. — The two next to the head, 



generally large and differing in shape from the 

 others. 



(2) The Flagellum. — All the other joints taken together. 



In the second section the antennae consist 

 generally of three joints (Plate III.), namely : — 



(3) The First yoint. — The one next to the head. 



(4) The Second yoint. 



(5) The Third yoint. — This is sometimes ringed, the 



rings showing like traces of joints, which indeed 

 they are, but closely adhering so as to appear as 

 one ringed joint (Plate III. 1-9). 



