OH. X] 



THE BODY-WALL AND MUSCLES 



209 



Segmental Muscles of the Abdomen. 



Th? muscles connected with the Internal Organs are dealt with in connection 

 with those organs. 



Nature and Mechanism of the Wing- Muscles. 



The Dragonfly differs from all other insects in the fact that 

 the great muscles of the synthorax are directly connected with 

 the wing-bases by means of tendons. In all other insects the 

 muscles bv means of which the action of the wings is controlled 



* c? 



are not directly connected with those organs, but are connected 

 with the notum. Those that pass from the notum to the sternum 

 are called iergo-sternals (or dorso-ventrals). Those that pass from 

 the notum to the pleurum are called laterals (or notopleurals). 

 From the table on p. 207 it will be seen that all the wing-muscles 

 of the Dragonfly, except one, are homologues of either tergo- 

 sternals or laterals. The direct attachment to the wing-bases 

 has been brought about by the development of special sclerites, 

 derived from the notum, in the formation of those bases. 



The adductor of the secondary anal vein is the exception mentioned 

 above. It has no homologue in any other insect (except perhaps 

 in the Locustidae). Its development is correlated with the peculiar 

 formation of the vein to which it is attached (p. 64). 



T. D.-F. 14 



