INTERNAL STRUCTURE. 



21 



part of the gaster, below the rectum. Forel distinguished this 

 apparatus into two types the Pulvinated and the Bourreleted 

 according to the form and arrangement of the different parts. 



The Pulvinated type is the more complicated, it is confined to 

 the Camponotinae, and in these forms more acid is stored. The 

 two free poison glands enter the distal end of the vesicle, where 

 they become a single tube, which is curled up into innumerable 

 windings, forming a cushion on the inside of the dorsal wall of the 



Vesicle 



Rectum 



Fig. 37. 



Repugnatorial glands 

 Repugnatorial glands of Tapinoma erraticum 



vesicle. This tube when unravelled is, according to Forel, quite 

 twenty centimetres in length. The duct of the vesicle opens in a 

 large orifice between certain vestiges of the almost obsolete sting. 

 The accessory gland opens into the duct of the vesicle, near its 

 termination. Janet suggests that the secretions of the accessory 

 gland, which are alkaline in character, are used to neutralize the 

 effect of the acid poison which may adhere to the ant's own body, 

 after it has used its poison, or sting, against an enemy. 



In the Bourreleted type, the apparatus is much simpler, the 

 vesicle is smaller and more globular, and its duct is more slender. 

 The free poison glands unite and enter the vesicle, where they form 



