158 



HARDWICKE'S SCIEN CE- GOS SIP. 



terminates above, with the anterior edge of which it 

 is connected by a membranous baud, which allows it 

 some freedom of motion. The internal plate of the 

 labrum which forms the roof of the mouth is con- 

 nected in front with the part just described, but is 

 prolonged behind almost the whole length of the 

 rostrum; it is grooved longitudinally along the centre 

 of the groove forming a cavity which can be greatly 

 enlarged by the action of two muscles which arise 

 one on each side of it for a considerable distance aud 

 are inserted above in the integument of the rostrum. 

 The lateral portions of this plate which are connected 

 with the floor of the mouth are very thin aud yield 

 ing, thus allowing easy play to the action of the 

 muscles in question. A pair of slightly curved aud 

 horny rods are developed in the membranous integu- 

 ment, one on each side of the external triangular 

 plate, which I suspect to be portions of the maxilla.* 

 A few sets arranged in pairs may be noticed between 

 them. 



Fig. |] 11. The opening of the mouth, x 120— alp, anterior 

 labial plate; < t< <, main false tracheas; 7iid, rudimentary 

 mandibles. 



II. The labium is the most complicated of the 

 organs of the mouth, and consists, as before stated, 

 first of the mentum. This is a somewhat quad- 

 rangular plate attached to the lower anterior border 



* Those who have read Mr. Lovvne's book on the Blow-fly, 

 will remember that he describes a portion of the maxillse as 

 united with the labrum, and he further says that the por- 

 tions so united are clearly the homologues of the terminal 

 lobes of the maxillse'in bees, the lobes referred.to being those 

 marked ?nx in his drawing of the maxillfe and labrum of a 

 Carpenter Bee, at p. 229 of Science-Gossip, in the number 

 for October last. If this is the] case,' I apprehend that in 

 the insect before us also the terminal lobes of the maxilla; 

 may be represented by the curved rods referred to in the 

 text, the remainder of these organs being recognizable in the 

 stout basal pieces from which the four-jointed maxillary palpi 

 spring. 



of the rostrum, its anterior edge being connected 

 with the base of the lobes. Its posterior border is 

 thickened and produced into a long slender rod, 

 which passes far back into the base of the head and 

 gives origin to a pair of muscles w^hich proceed to 

 the maxilla. A slight inversion of the integument 

 occurs between the rostrum and the mentum aud 

 again between this last and the base of the lobes. 



Fig. 113. Anterior labial 

 plate, X 210. 



Fig. 112. Pharynx and mouth cavity from above— lettering as 

 before, x 24. 



The floor of the mouth.* which is opposed to the 

 roof of the same before described, is almost wholly in- 

 cluded within the rostrum, along the whole length of 

 which it extends. A transverse section of it is some- 

 what crescent-shaped, the concavity being upper- 

 most. It is deeply channelled at the anterior portion, 



* I believe this to be the homologue of the posterior labial 

 plate described by Mr. Lowne at p. 46, though its connection 

 with the mentum is not so clear as in the Blow-fly, inasmuch 

 as the greater portion is internal, being entirely inclosed 

 within the rostrum. 



