668 



TONGUE OF FLY. 



This Ligula is extremely developed in the Fly kind, in which it forms 

 the chief part of what is commonly called the 'Proboscis' (Fig. 343) ; 



Fig. 343. 



Tongue of common Fly : — a, lobes of Ligula ; b, portion enclos- 

 ing the Lancets formed by the metamorphosis of the Maxillae : 

 c, Maxillary Palpi : — a, portion of one of the metamorphosed 

 Tracheae enlarged. 



and it also forms the ' Tongue' of the Bee and its allies (Fig. 344). 

 The Tongue of the Common Fly presents a curious modification 

 of the ordinary Tracheal structure (§ 525), the purpose of which is 

 not apparent ; for instead of its Trachea? being kept pervious, after 

 the usual fashion, by the winding of a continuous spiral fibre through 

 their interior, the fibre is broken into rings, and these rings do not sur- 

 round the whole tube, but are terminated by a set of arches that pass 

 from one to another (Fig. 343, A). — In the Diptera or two-winged 

 Flies generally, the Labrura, Maxilla?, Mandibles, and the internal 

 Tongue (where it exists) are converted into delicate Lancet-shaped 

 organs termed Setce, which, when closed- together, are received into 



