DE. F. LEUTHKEE ON THE ODONTOLABINI. 415 



My prolonged morphological studies have led me to the conclusion that the 

 remarkable species 0. (jazeJla, Fabr., is nearly related to the above species, notwith- 

 standing its great apparent differences. In 0. gazeUa the mandibles are always 

 monstrously developed both in large and small males for some reason which cannot 

 yet be even guessed at (PI. XCVI. fig. 10). The large head, the broad prothorax, 

 the long incurved front tibiae channelled in front, and the strongly developed prosternal 

 process make it probable that this species is derived from one in which the mandibles 

 were normally developed as in other species, and afterwards, during the insect's com- 

 petition with other species, developed into these extraordinary pincers. This view is 

 supported by a unique specimen in Herr van Lansberge's collection, in which the 

 mandibles are bilaterally and symmetrically developed, and have an inner branch in 

 the middle (PI. XCVI. fig. 10 b). The great pugnacity of this insect is manifested by 

 the many wounds which it has received in conflict with other males. The canthus is 

 bitten away, the central tooth of the right mandible is broken ofi", and there is an 

 indentation at the tip. These injuries have certainly been caused by the mandibles of 

 another individual, as the shape and character of the injuries clearly indicate. The 

 necessity for defensive organs may have resulted in the widening of the canthus in 

 both sexes. I have been led to this conclusion by the following considerations: — 

 (1) The geographical distribution corresponds to that of the last-mentioned species. (2) 

 Similarity of the females. (3) Resemblance of the amphiodont forms of 0. woUastoni 

 and 0. ludekingi (PI. XCIII. figs. 9, 11) in the shape of the head and in the structure 

 of the mandibles. (4) In all these species the rim of the elytra is black on the under- 

 surface. (5) The front margin of the prothorax in 0. lacordairii (PI. XCIV. fig. 2) 

 has a tendency to become narrowed in front. (6) In all the small forms the legs are 

 curved, and the front tibiae are channelled. (7) The canthus, if we imagine the 

 excavation to be filled up, would agree in all these species. Finally (8), agreement in 

 the form and size of the prosternal process. 



The characters of 0. gazeUa being once permanently fixed, it becomes easy to under- 

 stand how this species may have given rise to insular races, which were but slightly 

 modified at first ; and how a geographical subspecies, 0. iiicequalis, Kaup, distinguished 

 by the uniform dark colour of the elytra, might become differentiated in the island 

 of Nias (PI. XCVI. fig. 12). In this form the mandibles (fig. 12 a, b) remain apparently 

 unaltered, but the number of spines on the front tibiae is reduced. Unfortunately 

 the female of incequalis is stiU unknown, and we do not know whether its coloration 

 has become modified like that of the male. 



(v.) Group of O. castelnaudi. 



Although this group appears at first sight to contain very dissimilar species, a 

 thorough examination shows them to be more closely related to one another than their 

 external appearance, and sometimes variable coloration, might lead us to expect. In 



