RiCE-PEST OF BRITISH BURMA. 3 



external orifices (stigmata) of its tracheae in the cater- 

 pillar closed and functionally replaced by extensive 

 series of tracheal-gills or organs for extracting oxygen 

 from water, and presenting in the pupa stage a 

 special modification of the cocoon whereby, in a 

 manner at present not very clearly understood, air is 

 extracted from the water, and enters the body by three 

 pairs of the stigmata which at this stage are exceedingly 

 prominent and, moreover, open. Respiration by means 

 of the organs termed tracheal-gills (which are nothing 

 more than fine branches of a closed tracheal system ex- 

 tended into outgrowths of the surface of the body with 

 walls so thin and delicate that exchange of gases can 

 readily take place between the water and the closed 

 system of tubes), though the rule in several groups of 

 insects at one or more stages is yet so exceedingly rare 

 amongst Lepidoptera as to be quite exceptional ; only 

 two species of this immense order from all parts of the 

 world having hitherto been shown to possess such organs, 

 namely, the European Paraponyx stratiotalis, whose 

 habits, structure, and metamorphoses were admirably 

 described and delineated by the celebrated Swedish 

 naturalist Baron de Geer* about the middle of the past 

 century, and the Brazilian Cataclysta pyropalis, which 

 forms the subject of an interesting and well-illustrated 

 essay in last year's volume of Wiegmann's Archiv by 

 onef of the brothers of him whose philosophic researches 

 in biology have made the already famous name of Miiller 

 one of the best known to the science of our day. These 

 two forms, with the Palan Byoo, belong to the family 



* Memoires pour servir a l'Hist. des Insectes, 1752, vol. i, pp. 517-54.1, 



pl- 37- 



t Willi. MCiller-Blumenau, Ueber einige in Wasser lebende Schmet- 



terlingsraupen Brasiliens, in Arch. f. Naturgeschichte, 1884, Band i, 

 pp. 194-21 1, pl. xiv. 



