176 HVMENOPTERA 



CHAP. 



species are rather numerous, and the habits of several have been 

 described by Bates, who, however, was not acquainted with some 

 of the most peculiar features in their biology, these having been 

 since revealed by Belt and AY. Miiller. 



These ants are predaceous in their habits, and some of the 

 species travel in vast hordes ; they occasionally enter houses and 

 clear them of much of the vermin with which they may be 

 infested. They have no facetted eyes, some of the forms being 

 quite blind, while others have a pair of peculiar lenses in the 

 position normally occupied by the compound eyes. Usually 

 there are two castes of the workers, and in some species these are 

 very different from one another, the mandibles being in the 

 larger form very elongate, cylindrical and unfit for industrial 

 purposes, while the individuals of the smaller caste have the 

 outer jaws shorter, with their edges apposed and coadapted : in 

 other species individuals with mandibles differentiated from the 

 normal form do not exist. The nomad habits of these ants were 

 described by Bates, but the detection of their temporary resting- 

 places was reserved for Belt, who found that, after their plundering 

 raids, they retired to a place of concealment, and there clustered 

 t< >gether in a compact mass like a swarm of bees. Belt says : 

 " They make their temporary habitations in hollow trees and 

 sometimes underneath large fallen trunks that offer suitable 

 hollows. A nest that I came across in the latter situation was 

 open at one side. The ants were clustered together in a dense 

 mass, like a great swarm of bees, hanging from the roof, but 

 reaching to the ground below. Their innumerable long legs 

 looked like brown threads binding together the mass, which 

 must have been at least a cubic yard in bulk, and contained 

 hundreds of thousands of individuals, although many columns 

 were outside, some bringing in the pupae of ants, others the legs 

 and dissected bodies of various Insects. 1 was surprised to see 

 in this living nest tubular passages leading down to the centre 

 of the mass, kept open, just as if it had been formed of inorganic 

 materials. Down these holes the ants who were bringing in 

 booty passed with their prey. I thrust a long stick doWn to 

 tlic centre of the cluster and brought out clinging to it many 

 ants holding larvae and pupae." 



Turning now to the LnhnJuf, question: many American 

 species of this genus have long been known, though all of them 



