ABSTRACT OF THIS P.U>ER (bY J. G. NEEDHAM, 

 FOR AUTHOR, IN ABSENTIA) ISSUED BY THE 

 BIBLIOGRAPHIC SERVICE, OCTOBER 6 



THE GILL-CHAMBER OF DRAGONFLY NYMPHS^ 



STEPHEN G. RICH 



Entomological Laboratory of Cornell University 



FORTY-EIGHT FIGURES 



CONTENTS 



Introduction 317 



Material and methods 318 



Historical review 318 



The gill-chamber of Cordulegaster 320 



Features common to all forms 326 



Survey of the forms of rectum 328 



The anal valve 342 



The zygopteran rectum 343 



The intestinal ampulla of Zygoptera 344 



Physiological considerations 345 



Summary 345 



Bibliography 348 



INTRODUCTION 



Darwin calls attention to the remarkable differentiation of the 

 alimentaiy tract in the nymphs of dragonflies, mentioning the 

 adaptation of the foregut for chewing and the hindgut for res- 

 piration and propulsion. Probably most entomologists have 

 seen the elongate nymphs of some Aeschnid dragonfly spout 

 water from the rectum in a jet at the surface or have seen the 

 creature dart through the water under the propulsion of this 

 same jet. A nymph, placed in a watch-glass of water, in a few 

 minutes, when it has become quiet, will inhale and exhale 

 water through the anal opening; a little suspended matter 

 makes the currents quite clear. That the rectum is in these 

 forms much enlarged and that it is furnished with tracheal gills 

 is well known; the respiratory structures themselves have been 



'Contributions from the Entomological Laboratory of Cornell University. 



317 



