4 
by internal body fluids and converted into food. These 
first larvae tended by the queen develop into workers. 
As soon as these workers are mature, they start to forage, 
and from then on they and not the queen provide food 
for the colony. 
Caste Development 
One of the most interesting questions concerning 
ants is, why does one egg develop into a worker, another 
into a soldier, another into a winged, reproductive 
queen, and yet another into a winged, reproductive 
male? Entomologists who study ants have been sure 
for some time that some regulatory system determines 
the number of members of each caste produced within 
a colony. However, the mechanisms of this regulation 
are not clearly known as yet. The males arise from 
unfertilized eggs. This is true also of all ant relatives 
such as wasps and bees. The queens and worker castes 
develop from fertilized eggs. When an ant queen mates, 
she receives enough sperm to last her entire lifetime and 
keeps it stored in special glands inside her body. The 
major factor in caste formation, therefore, is the control 
of the development of fertilized eggs and does not in- 
volve heredity directly. 
The clue to the differential development of the eggs 
seems to be found in certain feeding habits. When a 
worker feeds a larva or the queen or a soldier, the 
worker licks the body of the individual it has just fed. 
Apparently the bodies of these creatures exude certain 
secretions that are sought and enjoyed by the workers. 
It is believed that these secretions are actually hormones 
that control the behavior of the workers, primarily 
influencing the kind of food that they feed to the larvae. 
It has been found that larvae fed a high-protein diet 
develop into soldiers, whereas those fed a low-protein 
diet develop into workers. Presumably, similar dietary 
differences will cause a larva to develop into a reproduc- 
tive queen. 
ANTENNA 
Fig. 2—Worker ant of the genus SCAPE 
Aphaenogaster, side view, showing terms 
used -for diagnostic parts. EYE 
PEDICLE 
MANDIBLE ——— 
LABIAL PALP 
MAXILLARY PALP 
TERMINOLOGY 
The anatomy of ants differs in several respects fro 
those of many other insects such as grasshoppers an 
beetles. As a result, several terms used in the followin 
keys may be unfamiliar to the general entomologist. T 
clarify these terms, many of them are indicated for th 
worker and queen caste in Fig. 2 and 3. Others a1 
listed in the short glossary below. ’ 
The most important morphological difference by 
tween ants and many other insects concerns the div 
sions of the thorax and abdomen. In ants (and a 
other Hymenoptera) the first segment of the abdome 
has become consolidated into the last or third segmer 
of the thorax and forms an indistinct dorsal plate calle 
the epinotum. This epinotal area sometimes bears di 
tinctive spines, epinotal spines. The main bulk of tl 
abdomen (called the gaster) is joined to the thora: 
epinotum by a constricted and often beadlike narro 
portion called the petiole, which may consist of one | 
two segments (the second and sometimes third tn 
segments of the abdomen). Unless one is referring sp 
cifically to the epinotal area, the epinotum and thor: 
together are usually referred to simply as the thora 
Abbreviated Glossary 
clypeus—The “upper lip” of the front of the he: 
(Fig 2* 3): 
dorsum—The upper surface or top. 
dorsal—Pertaining to the upper surface or top. 
frontal carina—A ridge of the head just to the me: 
side of the base of the antenna; this may be elevat 
or form an overhang over the base of the antenr 
funicle—The many-segmented portion of the anten 
beyond the scape or basal segment. 
mesal—On or toward the midline of the body. 
node—A projection or elevation on the dorsal surfa 
of one of the segments of the petiole. 
ABDOMEN— —— — 
GASTER 
