416 DR. F. LEUTHNER ON THE ODONTOLABINI. 
order to facilitate their study, we will divide them into three sections, and begin with 
the second. ‘The different male forms are arranged on Pl. XCYV. so as to admit of 
easy comparison. 
A, B. C. 
Mentum hairy. Mentum hairless. 
c =n : : 
O. eratus. O. castelnaudi. O. latipennis. 
O. sommeri. O. fratellus, 
a ae 
O. carinatus, Linn. 
O. brookeanus. 
Mentum and gula 
hairy 
IN 
| O. lowii. 
The females of this section (Pl. XCV. figs. 5, 10, 16) agree in appearance and colour 
with those of the two preceding groups. The coloration reminds us of 0. cwvera and 
O. wollastoni, in O. sommeri (figs. 10,11); in the variety (fig. 12) the yellow colour 
already extends to the sides of the prothorax, and is still more variable in 0. brookeanus 
(figs. 16, 17, 18). In O. castelnaudi, which is nearly twice as large, the elytra are 
almost entirely yellow, owing to the disappearance of the triangular spot, the last 
remains of which are seen in a small stripe at the base and another on the suture 
(fig. 5). 
In the males the black triangular spot on the elytra is reduced to a narrow black 
line on the suture, and the pale coloration extends to the sides of the prothorax, and 
even to the head and to the under-surface of the body. Apart from the immediately 
obvious similarity of the males, they present the following morphological resemblances, 
viz.: a large broad head, a short and very broad prothorax, long curved fore legs, with 
few spines, and in the telodont forms, a broad quadrangular epistoma-like clypeus, A 
character peculiar to all the species of this group is the hairy mentum, and in the 
three last species the gula is also hairy. Notwithstanding the difference of the man- 
dibles in the telodont forms (figs. 1, 13) (which are at present insufficiently known in all 
the species) they are remarkably similar, both in the priodont (figs. 8, 15), amphiodont 
(figs. 4, 7, 9, 14), and mesodont (figs. 2, 3, 6). This resemblance can only be accounted 
for by a common origin and hereditary descent, with a tendency to modification—a view 
which is likewise confirmed by their geographical distribution, for O. sommeri occurs 
in Banka (and Sumatra), and is intermediate between O. castelnaudi and O. brookeanus, 
which occur in Sumatra and Borneo, between which islands Banka is situated; and 
O. lowii, which is most nearly related to O. brookeanus, likewise occurs in Borneo. 
The amphiodont form of O. castelnaudi (Pl. XCV. fig. 4) easily leads us on to the 
male form of O. latipennis (Pl. XCVI. fig. 1) belonging to Section C, The shape of 
