The number of tarsal segments is reduced; often three, two or only one may be present instead of the typical insectan number five.
The fifth (distal) tarsal segment carries a median adhesive pad - the pulvillus - on either side of which is a claw.
This is a somewhat heterogeneous group, most of whose members are characterized by clubbed feelers and simple, unbroadened tarsal segments - usually five on each foot - but in some familie andenera the males have less than the normal number on the feet of one pair.
Rather smaller than a squirrel, with dusky brown fur, the tarsier has immense eyes, large ears, a long thin tail, tufted at the end, a greatly elongated tarsal portion of the foot, and disk-like adhesive surfaces on the fingers, which doubtless assist the animal in maintaining its position on the boughs.
But the legs carry peculiar spines, and the terminal tarsal segment is cup-shaped at the end; from this hollow a delicate bladder (fig.
I, Fore-leg and pro-sternum (S) ta, Tarsal segments.
Below the carpal and tarsal joints, the fore and hind limbs correspond almost exactly in structure as well as function.
In most insects the leg is built up of nine segments: (1) a broad triangular, sub-globular, conical or cylindrical haunch (coxa); (2) a small trochanter; (3) an elongate stout thigh (femur); (4) a more slender shin (tibia); and (5-9) a foot consisting of five tarsal segments.
The coat is remarkable for its density and compactness; the general colour of the head and upper parts being clove-brown, with more or less white or whitish grey on the under parts and inner surfaces of the limbs, while there is also some white above the hoofs and on the muzzle, and there may be whitish rings round the eyes; there is a white area in the region of the tail, which includes the sides but not the upper surface of the latter; and the tarsal tuft is generally white.
The bees which make up this group agree with the Sphecoidea in the short pronotum, but may be distinguished from all other Hymenoptera by the widened first tarsal segment and the plumose hairs on head and body.