The males are larger, and have the rostrum dilated at the end, and sometimes terminating in a good-sized pair of jaws.

I once saw two males fighting together; each had a fore-leg laid across the neck of the other, and the rostrum bent quite in an attitude of defiance, and looking most ridiculous.

Another time, two were fighting for a female, who stood close by busy at her boring.
They pushed at each other with their rostra, and clawed and thumped, apparently in the greatest rage, although their coats of mail must have saved both from injury.

The small one, however, soon ran away, acknowledging himself vanquished.

In most Coleoptera the female is larger than the male, and it is therefore interesting, as bearing on the question of sexual selection, that in this case, as in the stag-beetles where the males fight together, they should be not only better armed, but also much larger than the females.