62 MR J. G. GOODCHILD ON 
sharply defined in structure, for individuals of intermediate 
grades occur. All the work, however, is done by the 
individuals which have small heads, whilst those which have 
enormously large heads, the worker majors, are observed to be 
simply walking about, I could never satisfy myself as to 
the functions of these worker majors.... I think they serve in 
some sort as passive instruments of protection to the real 
workers.... The third order of workers is most curious of all. 
If the top of a small hillock, one in which the hatching 
process is going on, be taken off, a broad cylindrical shaft is 
disclosed at a depth of about two feet from the surface. 
If this be probed with a stick .. . . a small number of colossal 
fellows will slowly begin to make their way up the smooth 
surface of the mine. Their heads are of the same size as 
those of the former class of worker majors, but the point is 
clothed with hairs instead of being polished, and they have 
in the middle of the forehead a twin ocellus, a simple eye, 
of quite a different structure from the ordinary compound 
eyes on the sides of the head. This frontal eye is totally 
wanting in the other workers, and is not known in any other 
kind of ant. ... I never saw them under any other 
circumstances than those here related, and what their 
special functions may be I cannot divine.” I have quoted 
Bates at some length in connection with the Umbrella Ants, 
because the points noticed are not only of interest in them- 
selves, but seem to me to serve well to illustrate the fact 
that a high degree of specialisation has been attained in the 
case of many species of ants. This, I think, points to 
the high antiquity of this section of the Hymenoptera— 
a conclusion to which further reference will again be 
made. 
What the Saiiba Ant does with the leaves is a matter 
still open to question. Some have maintained that leaf- 
cutting ants use the leaves for the purpose of cultivating 
some fungi upon which the ants feed. It is likely enough: 
but no one seems to know for certain that such is the 
case. 
In connection with the destructive habit of leaf-cutting, 
another matter of interest arises, to which fuller reference 
will be made further on. 
