ANATOMY OF THE HONEY-BEE 189 



tern of air tubes, termed tracheae, which carry the air 

 to all parts of the body. When the body of an insect 

 is opened, the tracheae appear as silvery threads, on 

 account of the contained air. In the adult honey- 

 bee certain of the tracheae are greatly expanded so 

 as to form large air sacs. (Plate XXVI b, 2). 



The glands. r Fhose glands found in the body of 

 the honey bee that are of most interest to the prac- 

 tical bee-keeper are the following: 



In the larva there is a pair of long, tubular glands, 

 which secrete the silk of which the cocoon is made. 

 These glands open through a common duct, which 

 has its outlet near the mouth. 



In the adult worker bee there are four pairs of 

 glands opening into the mouth, which have been 

 much discussed by students of this subject. These 

 glands are designated both by number and by 

 name as follows: System I. or supracerebral 

 glands; system II. or postcerebral glands; system 

 III. or thoracic glands; and system IV. or 

 mandibulary glands. 



The supracerebral glands or system I. (Plate XXV, 

 Fig. 4, 1) are situated in the head above the brain. 

 They open by two openings in the floor of the mouth 

 cavity, one on each side. 



The postcerebral glands or system II. (Plate XXV, 

 Fig. 4, 2) are situated in the head behind the brain; 

 their outlets unite into a common duct which opens 

 on the middle line of the anterior end of the oeso- 

 phagus at the base of the tongue. 



The thoracic glands or system III. (Plate XXV, 



