6 C. HERBERT HURST. 



of tlie animal. It is broad from side to side, short from back to 

 front, while ventrally it is drawn out into a long process which 

 extends backwards under the thorax as far as the anterior part of 

 the abdomen, where it curves upwards. This process is made up of 

 what are usually spoken of as the " mouth-parts," including labrum, 

 epipharynx, one pair of mandibles, two pairs of maxillie, and the 

 hypopharynx. The second pair of maxilke are fused together to 

 form the labium. 



In describing an animal Avhich is coiled up so that head and tail 

 almost meet, the terms " dorsal," " ventral," " anterior," and "pos- 

 terior " are liable to be misleading. To avoid this as far as possible 

 I shall apply the terms to those parts to which they would be 

 respectively applicable in the fully-developed insect in the act of 

 sucking blood, i.e., I shall regard the general direction of the mouth- 

 parts as downward, their distal ends as ventral, and I shall speak of 

 the labrum as being in front of the mouth. 



From the sides of the epicranial region the antenna run outwards 

 to the sides of the thorax, and then downwards, one beneath the 

 anterior margin of each wing. The head and all its appendages are 

 immoveable during pupal life. 



The thorax is rounded, but somewhat compressed from side to 

 side. From the sides of its summit arise the respiratory siphons, 

 a pair of conspicuous organs whose position has led to the name 

 " horns " being applied to them. The wings are nearly flat oblong 

 plates, arising behind the bases of the siphons and extending down- 

 wards and backwards. Immediatel}' behind them are the halteres, 

 a pair of triangular plates enclosing the halteres of the future gnat. 

 I have endeavoured to show the forms of these parts in Fig. 1. 



The legs are almost completely hidden by the wings, but the 

 femur, tibia, and first joint of the tarsus of the first leg, and the 

 tibia and first joint of the tarsus of the second are visible (Figs. 1 

 and 2). 



The abdomen is flattened dorso-ventrally, and when at rest is 

 curved under the thorax. It is jointed and flexible, and forms with 

 the pair of large flat fins borne by its eighth segment the only 

 locomotor organ of the pupa, the wings and legs lying immoveable 

 and even adhering to one another, though they are easily separated 

 in specimens which have been kept in alcohol. 



