The Anatomy of Ants. By Sir John Lubbock, Bart. 127 
end in front. The front edge of the clypeus is sometimes straight, 
sometimes arched ; sometimes entire, sometimes provided with 
teeth. 
Behind the clypeus is the forehead. Posteriorly it passes im- 
perceptibly into the general upper surface of the head, but at the 
sides it ends in a sharp escarpment (Plate CXCII., Fig. 1, FF). 
These lateral edges are generally termed ridges (“ Stirnleisten,” 
Mayr), an expression which, however, scarcely gives a correct 
idea. The forehead is sometimes divided into two halves by a 
median line. Between the clypeus and the forehead there is in 
some species a small triangular piece or area frontalis — the stirnfeld 
of Mayr, aire frontal of Forel. 
Along the middle line of the under surface of the head, from the 
posterior end of the head to the base of the buccal organs, a strong 
ridge projects inwards. There is also on each side of the head a 
chitinous process or apophysis (Plate CLXXXIX., Fig. 2, I ; 
Plate CXC., Fig. 1, I), which, originating from the occipital ring, 
passes forwards and is attached to the anterior wall of the head 
near the base of the antennae. Towards the middle of the 
apophysis exists a wing like expansion, which, like the apophysis 
itself, serves as a basis of attachment for muscles. 
Plate CXCII., Fig. 1, represents the head of an ant ( Lasius 
jlavus), § , seen from above ; and Plate CXC., Fig. 1, that of the 
same species and sex seen from below. In the former, F are the 
so-called frontal laminae (stirnleisten of Mayr). They diverge 
as they pass backwards. In other species they are parallel, while 
in some cases they are curved like an S. 
The antennae rise, as just mentioned, under the ridges of the 
laminae frontales, sometimes close to the hinder edge of the clypeus, 
sometimes a little farther back. 
They consist of a short spherical basal piece, a long shaft, 
known as the scape, and a flagellum of from six to seventeen 
(generally, however, from ten to thirteen) short segments, the 
apical ones sometimes forming a sort of club. The number of 
segments is generally different in the males and females. 
i. On each side of the head are the large compound eyes. The 
number of facets differs greatly in different species, and in the 
different sexes, the males generally having the greatest number. 
Thus, in Formica pratensis there are, according to Forel, in the 
males about 1200 in each eye, in the fertile females between 800 
and 90X3, in the workers about 600. Where the workers vary 
in size they differ also in the number of facets. Thus, again 
following the same authority, the large workers of Campouotus 
ligniperdus have 500, the smaller ones only 450 ; while in the 
Harvesting ant (Atta barbara) the contrast is even greater, the 
large specimens having 230, the small ones only from 80 to 00. 
