VI 



ANTENNA TA WINGS 



455 



become short stalked vesicles of considerable size, which may be compared with the 

 protruded coxal sacs of the Thysanura. A respiratory function has without sufficient 

 foundation been ascribed to both these structures. 



Considering the widespread occurrence of rudimentary abdominal feet in the 

 Embryos of winged Insects we are justified in asking the question, whether the 



B 



(L 



-P9 



FIG. 316. A and B Hydrophilus embryos with the rudiments of extremities (after Heider). 

 In the somewhat older embryo, B, the rudiments of abdominal feet, which disappear later, can be 

 very distinctly seen ; a, anal aperture ; an., antenna; g, rudiment of the ventral ganglionic chain; m, 

 oral aperture, md, Mandible ; mxi, 1st maxillse ; mx%, 2d maxillae (rudiment of the lower lip) ; pi, 

 f>ii P& thoracic pairs of legs ; p, p^, p?, p 9 , rudiments of extremities of the 1st, 2d, 4th, and 6th 

 abdominal segments ; st, stigmata ; vie, procephalon. 



truncated feet (anal feet) of the larvse of butterflies and wasps are not rather the 

 remains of real limbs than new formations. 



C. The Wings. 



Wings are altogether wanting in the Myriapoda. Among the 

 Hexapoda the Apterygota, as their name implies, are entirely wingless. 

 Since neither the adult Apterygota nor the embryos at any stage of 

 their development have wings or organs belonging to wings, we are 

 justified in assuming that their ancestors also were wingless, in short 

 that the wingless state is as much the original condition here as in the 

 Myriapoda and Protmcheata. This assumption is not without support 

 from other points in their constitution. All other Hexapoda, however, 

 are typically provided with wings, and originally indeed with 2 pairs, 

 and although within the different orders of the Pterygota the wings 



