136 



continues on through the neck, and supplies the 

 head with numerous large branches. 



2. A large branch passes upwards and back- 

 wards along the edge of the meso-scutum, and 

 gives off branches which supply the wing muscles. 

 A smaller branch also passes forwards and supplies 

 the muscles of the thorax. 



3. The largest trachea in the body (main 

 trachea) passes downwards, backwards, and in- 

 wards, so as to lie on either side of the anterior 

 portion of the alimentary canal. Numerous 

 branches are given off from this trunk to the 

 thoracic muscles, the alimentary canal, and legs. 

 Posteriorly the trunk is continuous with a 

 trachea passing forwards from the second thoracic 

 spiracle, thus forming on either side a large 

 tracheal loop. 



Large tracheae also pass inwards from the 

 posterior thoracic spiracles. 



1. Branches pass forwards and join in a 

 loop with the main trachea, also backwards to 

 join the abdominal system. 



2. Branches pass downwards to the meta- 

 thorax and posterior pair of legs. 



3. Branches pass inwards to the muscles and 

 mid-gut. 



From each abdominal spiracle a short thick 

 trunk passes inwards, which gives rise to the 

 following branches : — 



A dorsal branch ramifying beneath the 

 tergum and joiniiig the branch of the opposite 

 side. 



A sternal branch supplying the sternal plate 

 and muscles, also joining the branch of the other 

 side. 



