_Pithecus lar_ (nec L.), Geoffr., Ann. Mus., xix., p. 88 (1812).
_Hylobates agilis_, F. Cuv., Hist. Nat. des Mammif., Sept. 1821, pls. v.,
vi.; Müller, Tijdschr. Nat. Gesch., ii., p. 326 (1835); Martin, Mammif.
Anim., p. 416 (1841); Fry, P. Z. S., 1846, p. 11; Gray, Cat. Monkeys
Brit. Mus., p. 12 (1870); Schl., Mus. Pays-Bas, vii., p. 17 (1876);
Anderson, Zool. Res. Exped. Yun-nan, p. 9 (1878; with full synonymy).
_Pithecus agilis_, Desmar., Mamm., p. 532 (1820).
{152}_Simia lar_ (nec L.), Raffl., Tr. Linn. Soc., xiii., p. 242 (1822).
_Hylobates lar_ (nec L.), F. Cuv., Hist. Nat., Mamm., pls. 7, 8 (1824);
Blyth, J. A. S. Beng., xliv., ex. no., p. 2 (1875).
_Hylobates variegatus_, Temm., Monogr. Mamm., i., p. xiii. (1827); Wagner
in Schreb. Säugeth. Suppl. v., p 16 (1855); H. O. Forbes, Nat. Wand.
East. Arch., p. 156 (1885).
_Hylobates rafflesii_, Is. Geoffr., Cat. Méth. Primates, p. 8 (1851);
Gray, Cat. Monkeys Brit. Mus., p. 11 (1870).
_Hylobates pileatus_, Gray, P. Z. S., 1861, p. 136, pl. xxi.; id., Cat.
Monkeys Brit. Mus., p. 10 (1871); Anderson, Zool. Res. Exped. Yun-nan, p.
6 (1878).
CHARACTERS.--Face black; colour entirely black, but becoming brown on the
back and sides, and with a white superciliary band, and sometimes ashy-grey
cheeks.
This is the typical form of the species in Mid-Sumatra, where the present
writer had the opportunity of examining it alive. It was with difficulty
distinguished from _H. syndactylus_, except from its size and the presence
of the white superciliary band.
Other specimens (but none of them met with to the south of the Moesi river
by the present writer) have been described, with the occiput, the back from
immediately behind the shoulders, the flanks, the hips, and the outer
surfaces of the fore- and hind-limbs, pale yellow. The shoulders, chest,
and belly, and the inside of the limbs and feet dark brown; eyebrows and
whiskers pale grey. (_Anderson._)
The variety described as _H. pileatus_ is distinguished by a black cap-like
patch on the top of the head; the chest, throat, and belly black; the back
of the head, the upper surface of the body, the limbs and area round the
black cap grey. This variety may also be entirely white, except for the
coronal cap {153}and chest being black, and the back brown; or the
pervading colour may be brown, the sides of the face and the under surface
black, and the whiskers white. The index and middle fingers are
occasionally webbed together.
All the hairs on the arm and fore-arm converge towards the wrist.
DISTRIBUTION.--This species is confined to Sumatra and to Siam. In the
former country it is known by the name of "Ongka" by the Malays, who, with
the keen powers of observation they possess in regard to all natural
objects, recognise two varieties, the white or yellow variety--"Ongka
putih," and the black one--"Ongka itam" (_H. rafflesi_). The capped variety
(_H. pileatus_) with its variously coloured forms inhabits Siam.
HABITS.--The habits of the "Ongka" are very similar to those of the
Wau-wau, or the Siamang (_H. syndactylus_). The natives, however, aver that
it is much more silent, rarely howling as either of these other two species
do. They are also seen generally in quite small troops, and often in pairs
only.
"It is almost impossible," writes Mr. Martin of a specimen that lived
formerly in the Zoological Gardens, "to convey in words an idea of the
quickness and graceful address of her movements: they may, indeed, be
termed aërial, as she seems merely to touch, in her progress, the branches
among which she exhibits her evolutions. In these feats her hands and arms
are the sole organs of locomotion; her body hanging as if suspended by a
rope, sustained by one hand (the right, for example), she launches herself
by an energetic movement to a distant branch, which she catches with the
left hand. But her hold is less than momentary; the impulse for the next
{154}launch is acquired; the branch then aimed at is attained by the right
hand again, and quitted instantaneously, and so on, in alternate
succession. In this manner spaces of twelve and eighteen feet are cleared
with the greatest ease, and uninterruptedly for hours together, without the
slightest appearance of fatigue being manifested; and it is evident that if
more space could be allowed, distances very greatly exceeding eighteen feet
would be as easily cleared.... Sometimes on seizing a branch in her
progress, she will throw herself, by one arm only, completely round it,
making a revolution with such rapidity as almost to deceive the eye, and
continue her progress with undiminished velocity. It is singular to observe
how suddenly this Gibbon can stop, when the impetus given by the rapidity
and distance of her swinging leaps would seem to require a gradual
abatement of her movements. In the very midst of her flight a branch is
seized, the body raised, and she is seen, as if by magic, quietly seated on
it, grasping it with her feet.... A live bird was let loose in her
apartment; she marked its flight, made a long swing to a distant branch,
caught the bird with one hand in her passage, and attained the branch with
her other hand; her aim, both at the bird and the branch, being as
successful as if one object only had engaged her attention. It may be
added, that she instantly bit off the head of the bird, picked its
feathers, and then threw it down, without attempting to eat it."