THE HIDDEN TYPE OF WING-GROWTH 141 



The pupal stage of the caddis-flies 1 (Trichoptera) is also 

 noteworthy, exhibiting special adaptations to life under water. 

 It has been mentioned (p. 122) that the larvae of these insects 

 live in cases or " houses ", composed of fragments of vegetable 

 matter or small stones fastened together by silken threads, 



FIG. 82. 



Pupa of Caddis-fly (Stenophylax) , dorsal view, x 8. b, 

 mandible of caddis-pupa (Sericostoma). x 50. c, fringed 

 foot of caddis-pupa (Potamorites). x 6. d, clawed foot of 

 caddis-pupa (Ptilicolepus). X 24. After Thienemann, Biologic 

 der Trichopteren-Puppe. 



and that they breathe by means of tubular gills. Before 

 pupation the larva shortens its case and constructs a wall 

 at the end formerly open, leaving, however, apertures for the 

 passage of water-currents which bathe the gills situated in 

 series on the abdominal segments ; and it is of importance 



1 A. Thienemann : " Biologic der Trichopteren-Puppe ". Inaug. Dissert. 

 Greifswald. Jena, 1905. 



