20 WORKERS— SOLDIERS. 



tion, and a second with immense heads provided with 

 very large jaws. This differentiation of certain indi- 

 viduals so as to adapt them to special functions seems 

 to me very remarkable ; for it must be remembered 

 that the difference is not one of age or sex. The large- 

 headed individuals are generally supposed to act as 

 soldiers, and the size of the head enables the muscles 

 which move the jaws to be of unusual dimensions ; but 

 the little workers are also very pugnacious. Indeed, 

 in some nests of Pheidole megacephala, which I had 

 for some time under observation, the small workers 

 were quite as ready to fight as the large ones. 



Again, in the genus Colobopsis Emery discovered 

 that two ants, then supposed to be different species, and 

 known as Colobopsis truncata and C.fuscipes, are really 

 only two forms of one species. In this case the entrance 

 to the nest is guarded by the large-headed form, which 

 may therefore fairly be called a soldier. 



Savage observed among the Driver Ants, where also 

 there are two kinds of workers, that the large ones 

 an'anged themselves on each side of the column formed 

 by the small ones. They acted, he says, evidently the 

 part of guides rather than of guards. At times they 

 place ' their abdomen horizontally on the ground, and 

 laying hold of fixed points with their hind feet (which 

 together thus acted as a fulcrum), elevate the anterior 

 portion of their bodies to the highest point, open wide 

 their jaws, and stretch forth their antennse, which for 

 the most part were fixed, as if in the act of listening 



