The Development of the Wings of a Caddis-fly 

 Platyphylax designatus Walk. 



By 

 \Vm. S. Marshall. 



With 6 Text figures and Plates XXVII— XXIX. 



There have been a considerable number of papers written con- 

 cerning the development of the wings of insects but, of the work des- 

 cribed, only a very small amount has been given to the organs of flight 

 in the Trichoptera. Pictet (13) figures (pl. II, fig. 16) a ventral view 

 of a pupa of Phryganea striata still enclosed in the last larval skin most 

 of which has been removed, the developing wings are external and 

 lie close to the body of the pupa at either side. 



The earliest account of the development of the wings of the Tri- 

 choptera is by Dewitz (3), this paper does not contain a continuous 

 account of one species but of two species at different stages of deve- 

 lopment. Dewitz describes the first appearance of the wings as above 

 the insertion of the leg and behind a group of hairs. He noted that 

 as the larva grew the wing rudiment became larger and its longitudinal 

 axis became more perpendicular. The invagination of the wall of 

 the hypodermis to form the rudiment is followed by a Prolongation 

 of the inner wall of the adjacent cuticular layer and there is thus 

 formed a hard supporting prop for the developing wing. Dewitz 

 says that the wing is thrown out of the pocket just before pupation 

 when the larva closes its case. During pupation the tracheae grow 

 into the wing. 



A year later Poletajeff (14) published a paper on the development 

 of the wings of the caddis-flies which account was written in Russian. 

 The plate shows two wing rudiments evidently taken from young 

 larvae, another after the wing has become external. There is also a 

 section through a wing rudiment. 



