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cases the prothoracic spiracles show a different number of lobes in the same 

 larva, e.g. one spiracle has seven, the other eight lobes (figs. 20-24). 



The post-abdominal spiracles are borne on two tubercles arising from the 

 terminal segment. These tubercles are surrounded by a chitinous hoop which 

 is open and flattened on the inner side. Each tubercle is again bilobed, each 

 secondary lobe opening to the exterior by two slits. Thus within the chitinous 

 hoop there lie four slits. These slits are surrounded by oval peritremes whose 

 internal border is dentate. The peritremes lie so that their axes converge 

 towards the inner border of the collar. The spiracle tubercle shows two white 

 spots, the openings of perispiracular glands (fig. 17). 



The spiracles communicate with the tracheal trunks through a "felt- 

 chamber" which is a short tube filled with a spongy chitinous structure. 



On the ventral surface of the last abdominal segment lies the anus in the 

 form of a cleft with a protuberance on each side. The posterior end of the larva 

 moves freely in the chitinous funnel, and, as far as has been observed, the 

 post-abdominal spiracles are never closely adpressed to the host trachea but 

 the air from the host trachea is drawn into the chamber formed by the adhering 

 chitinous funnel where it is at the disposal of the larva. 



Bucco-Phaeyngeal Apparatus. 



The complete masticating apparatus of the mature larva of Bucentes 

 geniculaia consists of a number of paired sclerites, the members of each side 

 articulating with one another to form a united whole (figs. 12 and 13). 



Overhanging the oral aperture is a pair of strong curved hooks, the 

 mandibular sclerites. Dorso-posteriorly these have -a dentate process, while 

 ventro-laterally they bear a blunt wedge-shaped process. A ventral view 

 shows the mandibular sclerites to be united by a cross bar. Each ventro- 

 lateral process is perforated by a minute pore. 



Articulating with the posterior border of the mandibular sclerites are the 

 hypostomal sclerites which are united ventrally by a transverse bar. Between 

 the mandibular and hypostomal sclerites there lies ventrally a fused dentate 

 sclerite which is perforate. 



The posterior extremities of the hypostomal sclerites articulate one on each 

 side with the cephalo-pharyngeal sclerites, which have each a slight anterior 

 rectangular prolongation, joining it to the hypostomal sclerite of its side. 

 The cephalo-pharyngeal sclerites are prolonged dorsally, into wing-like pro- 

 cesses which are perforate near their outer edges, and ventrally, into a stout 

 somewhat rectangular posterior process which has a curved incision at. its 

 extremity. 



The cephalo-pharyngeal sclerites articulate ventrally with a broad chitinous 

 plate, the floor of the pharynx, as do also the extremities of the posterior 

 ventral processes. 



The Puparium (fig. 14). The puparium is brown in colour, barrel-shaped 

 and with clearly marked segments. Each segment bears a double series of 



