A. W. Rymer Roberts 



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on either side of the body of the larva. At the point of contact of the 

 atrium and the trachea there is a sUght thickening around the latter. 



There are no taenidia lining the atrium, but its epithelium is com- 

 posed of irregular pentagonal cells, which are plainly visible in a stained 

 preparation, even of an exuvia. Miall and Denny (lO) have described a 

 very similar chamber with polygonal epithehal cells as existing just 

 within the stigmatic orifices of cockroaches and Boving(3) has described 

 it in the larvae of Donacia, Hister and an Elaterid from Java. 



The margins of the two stigmatic orifices are thickened into a peri- 

 treme of stout brown chitin, the surface of which, as well as the sides and 



Fig. 3 a. Transverse section of larval spiracle. 

 b. Larval spiracle as seen from beneath. 



jSc. =Scar; 5.= Septum; i?0. = Respiratory orifice; i^.= Floor of spiracle; AC. 

 = Antechamber; J[<.= atrium; Tr. = Trachea; C. = polygonal cells of atrium (a few 

 only shown). 



floor of the orifice itself, is transversely corrugated. A fine, somewhat 

 irregular, suture separates the peritreme of each orifice on the surface 

 of the septum. At the anterior and posterior ends of the orifice, the 

 peritreme is narrower, especially at the posterior end. In young larvae 

 of the first and second instars the peritreme is invisible at the anterior 

 end, though present as a narrow ridge of chitin at the posterior end. 

 The corrugations already mentioned which project as small teeth on 

 either side of the stigmatic orifices, vary in number according to the 

 instar. In the final instar they number some 47 in the thoracic and 40-43 

 in the abdominal spiracles. In the young larva of the first instar they 



