Differences between adult males and females of _T. ornata_ have been
mentioned in several places in the preceding discussion of growth and
development. Several sexual characteristics--greater preanal length,
thickened base of the tail, slightly concave plastron, and smaller
bulk--are found also in males of many other kinds of emyid turtles.
From females, males of _T. ornata_ are most easily distinguished by
the bright colors of their eyes, heads, and antebrachial scales. An
additional, distinctive characteristic of males is the highly modified
hind foot. The first toe is greatly thickened and widened; when the
foot is extended, the first toe is held in a horizontal plane nearly
at right angles to the medial edge of the plantar surface (Fig. 21).
The hind foot of females is unmodified in this respect. Males tend to
have heavier, more muscular hind legs than females.
The bright colors of males are maintained throughout the year and do
not become more intense in the breeding season. Males of _T. o.
luteola_ become melanistic in old age whereas males of the subspecies
_ornata_ do not. In old males of _luteola_ the skin becomes dark gray,
bluish, or nearly black and much of the bright orange or red of the
antebrachial scales and the green of the head is obliterated; the iris
may also darken but in most specimens it retains some red. Females of
_luteola_ tend also to darken somewhat in old age but not so much as
males; females of _ornata_ do not. Table 4 summarizes the more
important secondary sexual characters of _T. ornata_.
TABLE 4.--A Summary of Sexual Dimorphism in _Terrapene ornata_.
============+============================+==============================
CHARACTER | MALES | FEMALES
------------+----------------------------+------------------------------
Head | Snout truncate in lateral | Snout relatively round in
| profile, top of head and | lateral profile; front of
| front of maxilliary beak | maxillary beak not forming
| forming an angle of nearly | right angle with top of head;
| 90A deg.; head yellowish green | head dark brown, distinct
| to bluish green; markings | pale markings on head and
| on head and neck reduced; | neck; head commonly spotted
| head never spotted dorsally| dorsally (Pl. 25, Figs. 5
| (Pl. 11, Figs. 7 and 8). | and 6).
------------+----------------------------+------------------------------
Iris | Red | Yellowish brown
------------+----------------------------+------------------------------
Hind legs | Heavy and muscular; first | Not especially heavy or
| toe turned in, thickened, | muscular; first toe, if
| and widened (Fig. 21). | turned in, never thickened
| | or widened (Fig. 21).
------------+----------------------------+-----------------------------
Forelegs | Centers of antebrachial | Centers of antebrachial
| scales bright orange or | scales yellow, pale orange,
| red. | or brown.
------------+----------------------------+-----------------------------
Carapace | Relatively lower, length | Relatively higher, length
| contained in height (48 | contained in height (94
| specimens) .58 times | specimens) .50 times
| (A+- .005[sigma]m, range, | (A+- .005[sigma]m,
| .50 to .69). | range .44 to .60).
------------+----------------------------+------------------------------
Plastron | Ordinarily slightly | Flat or convex, never
(hind lobe)| concave. | concave.
------------+----------------------------+------------------------------