106 PAUL S. WELCH. 



RESPIRATION. 



One of the problems which confront an insect possessing an 

 aquatic stage is that of securing the requisite amount of oxygen. 

 Those few genera of Lepidoptera which are unique in having 

 aquatic larvee have solved the problem in one of two ways: (i) 

 by the utilization of the dissolved oxygen, either by means of 

 gills or through cutaneous respiration, or (2) by making periodic 

 trips to the surface in order to secure the oxygen from the air. 

 Each of these adaptations calls for distinctly differentiated 

 structures and each is accompanied by interesting habits and 

 activities. Bellura melanopyga has solved the oxygen problem 

 by a peculiar development of the spiracles and by making periodic 

 trips to the surface. A careful study has been made of this 

 adaptation and the results will be given in some detail. 



Respiratory Apparatus. Paired spiracles are present on I, 

 IV, V, VI, VII, VIII, IX, X, and XI. All, exclusive of the 

 pair on XI, are similar in size, are elliptical in shape, are lateral 

 in position, and have the long axis vertical. Somites I-X are 

 similar but XI-XIII form the chief structural differentiation 

 accompanying this aquatic habit. XII is very short, being 

 only about one-fourth as long as XI, and its dorsal surface 

 is depressed considerably below the corresponding surface of XI. 

 The dorsal, posterior margin of XI bears two large, elliptical 

 spiracles, one on each side of the median line. They are placed 

 obliquely, the long axis being inclined about forty-five degrees 

 from the vertical. They are at the posterior termini of the lateral, 

 longitudinal tracheal trunks, opening directly into them. All 

 other spiracles have short branches leading into the longitudinal 

 trunks. Each of the terminal spiracles on XI opens into a 

 somewhat enlarged region of its respective longitudinal trachea 

 which probably serves as a reservoir for the supply of air which 

 is carried below the surface by the larva on its downward trips. 

 XIII is somewhat larger than XII and forms the cauda. Its 

 dorsum is on the same level with that of XII and the lateral 

 margins converge caudad. 



The Leaf-Feeding Period. During the leaf-feeding period res- 

 piration is carried on in the same way as in terrestrial lepidop- 

 terous larvae. Each larva is working in a mine in the leaf but 



