176 HYMENOPTERA 



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

 described l)y Bates, who, however, was not acquainted with some 

 of the most pecuHar features in their l)iology, these having been 

 since revealed l)y Belt and W. Mliller. 



These ants are predaceous in their haljits, 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 l^e 

 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 unlit 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 tliat, after their plundering 

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

 together in a compact mass lilce a swarm of bees. Belt says : 

 " They make their temporary habitations in hollow trees and 

 sometimes underneath large fallen trunks that oifer suital)le 

 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 l)elow. Their innumerable long legs 

 looked like brown threads binding together the mass, which 

 must have been at least a culiic 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. I was surprised to see 

 in this living nest tul)ular 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 

 l)Ooty passed with their prey. I thrust a Ljng stick down to 

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

 ants holding larvae and pupae." 



Turning now to the Zahidus question : many American 

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



