Jan., 1922 the tracheal branches of insects 89 



EXPLANATION OF PLATE. 



Fig. 1. Lateral view of Lestes naiad, male, showing the homologies of the somatic 

 tracheal branches. 



Fig. 2. Ventral view of Lestes naiad. 



Fig. 3. Hypothetical, primitive segmental tracheal organs. By the fusion of 

 a series of such the Lestes trachial system may have been developed. 



LIST OF ABBREVIATIONS USED IN THE ILLUSTRATIONS. 



sp. — spiracle. 



spp. — spiracular pit. 



spt. — spiracular tnmk. 



St. — sternal trachea. 



dt. — dorsal trunk. 



latt. — lateral trunk. 



vt. — ventral trunk. 



It. — leg trachea. 



pt. — pleural trachea. 



gt. — ganglionic trachea. 



agt. — accessory ganglionic trachea. 



asc. — anterior spiracular connective. 



adc. — anterior dorsal connective. 



pdc. — posterior dorsal connective. 



alt. — anterior latero-tergal trachea. 



pit. — posterior latero-tergal trachea. 



tadc. — tip of anterior dorsal connective. 



tpdc. — tip of posterior dorsal connective. 



