632 aiR. G. S. COTTERELL ON THE LIFE-HISTORY 



the thinly-cliitinised membranes between the coxse and thorax. 

 The fly is then turned completely round, bringing the ventr'al 

 surface of the abdomen uppermost and the head in si posterior 

 position. The contents of the abdomen are then sucked out 

 through punctures between the sternites. 



This order of feeding is invariably carried out, but, when food 

 is abundant, the parts are only partially sucked out, the abdomen 

 often not being touched. 



Attraction for more food from one victim apparently ceases 

 when struggling has ceased. 



Both sexes are very strong in flight and are capable of flying 

 short distances, grasping flies as large as themselves. 



Adult Mouth-parts. 



On account of its predaceous habits the mouth-parts are 

 modified accordingly. 



Externally the proboscis is of the Muscid type, i. e. the ordinary 

 labella consisting of the fused inner lobes of the labium, the 

 23seudo-trache8e, the labrum-epipharynx, hypopharynx, and maxil- 

 lary palpi. These structures are identical with those found in 

 Musca domestica or Galliphora erythrocephala, in which the pro- 

 boscis is adapted for licking. The only modifications due to its 

 predaceous habit are found in the internal chitinised structures 

 of the labellum, or oral disc, and haustellum. 



The structure of the rostrum, or proximal p)ortion of the 

 proboscis, is identical with that of G. erytlirocephala as described 

 by Lowne. The main chitinised structure is the fulcrum (text- 

 fig. 2, «) enclosing the phaiynx. This has been compared by 

 Kraepelin to a Spanish stirrup-iron with a double foot-plate, the 

 foot-plate being posterior and the toe at the lower end. The 

 whole structure of the rostrum resembles that of a truncated 

 cone with the apex downwards. 



The haustellum or arm of the proboscis is cylindrical in shape. 

 Proximally it is attached to the lower end of the i-ostrum, and 

 distally to the oral disc. It is enclosed on its lateral and 

 ventral sides by a convex sclerite, the theca (text-fig. 2,^). This 

 ai'ticulates proximally with the fulcrum and distally with the 

 f urea (text-fig. 2, (/), a tri-radiate sclerite forming the chief 

 internal skeletal structure of the oral disc. 



The la,brum-epipharynx (text-fig. 2, d) and hypopha,rynx (text- 

 fig. 2, e), enclosing the salivary duct, lie over the dorsal portion of 

 the haustellum as in the House-fly. 



The oral disc consists of two lobes united posteriorly by a ball- 

 and-socket joint, each grooved on its oral surface by a number of 

 pseudotracheaB (text-fig. 2, k). The oral aperture is situated 

 between the lobes at their point of junction. A space below the 

 mouth is kept open by a pair of sclerites, the discal sclerites 

 (text-fig. 2, A), deeply embedded in the oral disc. These sclerites 



