30 DIPTERA OF AUSTRALIA, 



meto/mera, the upper portion of which, combined with the epi- 

 pluxryrvx, forms the lahrum ; its lower part is generally separated 

 from the hypopharynx, and forms the labium. Behind this is the 

 second metamera, that of the maxillce, and the maxillary lobes are 

 simply processes of it, and not jointed organs; the raaxillary pdlin 

 are generally similar, only being jointed to the metamsra, and 

 themselves articulated in Culex and Tipula. The third and last 

 metamera, that of the mandibles, is generally separated from the 

 preceding, though its hinder part its strongly soldered to the 

 cephalic plate : it is, however, never exposed. 



II. Tits tliorax. 



The riiesothorax is very largely developed in this order, being so 

 much larger than the prothorax and metathorax that it forms the 

 greatest part of this division of the insect's body ; on account of 

 this it is designated the tliorax, while different names are bestowed 

 upon characteristic parts of the jrrotli/jrax and metatloorax. The 

 former frequently forms a neck-like prolongation which bears the 

 head, and is then called the neck {collum). In some cases the 

 fore corners of the mesothorax or the shoulders (humeri) are 

 covered by a lobe of the prothorax (lobus prothoracis humeralisi, 

 distinctly separated from the mesothorax ; if this lobe be so 

 soldered to the mesothorax that it is impossible to detect a distinct 

 limit between them, except in general by their colour or hair, it 

 is styled the shoulder callosity (callus humeralisj. When the 

 prothorax applies closely to the anteiior border of the mesothorax, 

 it has then the name of collar (colla/re). An important character, 

 in its presence or absence, is a transverse furrow (sutura trans- 

 versalis) frequently found crossing the middle of the upper side of 

 the mesothorax, and terminating on each side just before the base 

 of the wing. On each side of the breast — the breast side (jdeura) 

 — there is beneath the shoulder a sjjiracle (stigma 2>'>'ot/toracisJ. 



The scutcheon (scutellum) is separated from the back of the 

 mesothorax by a furrow, and is situated between the wings. 

 A part of the metathorax is to be seen beneath the scutellum, 

 called the metanotum; this is generally found descending obliquely, 

 often very convex, and on each side with a more or less inflated 



