PHOTOGENIC ORGANS AND EMBRYOLOGY OF 

 LAMPYRIDS 



F. X. WILLIAMS 



TEN PLATES 



CONTENTS 



Introduction . . ; 145 



Origin and development of the photogenic organs 146 



Structure of the photogenic organs ' 149 



Development of the photogenic organs in the adult Photinus consanguineus. 150 



Development of the larval photogenic organs in Photuris pennsylvanicus. '. 161 



Physiology of the photogenic organs 164 



Notes on the embryology of Photuris pennsylvanicus 172 



The pleuropods or first abdominal appendages in the embryos of Photuris and 



Photinus ' 178 



Summary 181 



Bibliography 185 



INTRODUCTION 



This paper is a part of the results of two years work at the 

 Bussey Institution of Harvard University, on the habits, struc- 

 ture and development of two common fireflies, Photuris penn- 

 sylvanica and Photinus consanguineus. The first of these fur- 

 nished nearly all of the embryological material and the second 

 was the more advantageous for the study of the development of 

 the photogenic organ of the adult. Not much attention was 

 paid to the physiological aspects of the problem. 



The material obtained was studied both in the living state 

 and in sections. Most used for killing the embryological mate- 

 rial was hot water followed by increasing strengths of alcohol. 

 Larvae, pupae and adults were first immersed in hot water and 

 then in warm Kahl's fluid (Water, 30 parts; 96 per cent alcohol, 

 15 parts; formalin, 6 parts; glacial acetic acid, 1 part). Usu- 

 ally the material was imbedded in paraffin, but when the chitin 

 was very thick, celloidin was used. Embryos were usually 

 stained in toto with borax carmine; the sections with Heiden- 



145 



JOURNAL OF MORPHOLOGY, VOL. 28, NO. 1 



