The Descent of Man

the males, the rudiments of the upper horns on
the females would not have been thus obliterated.
[Fig. 23. Bledius taurus, magnified. Left-hand
figure, male; right-hand figure, female.]
The cases hitherto given refer to the Lamellicorns,
but the males of some few other beetles,
belonging to two widely distinct groups, namely,
the Curculionidae and Staphylinidae, are
furnished with horns—in the former on the
lower surface of the body (66. Kirby and Spence,
'Introduction to Entomology,' vol. iii. p.
329.), in the latter on the upper surface of the
head and thorax. In the Staphylinidae, the
horns of the males are extraordinarily variable
in the same species, just as we have seen with
the Lamellicorns. In Siagonium we have a case
of dimorphism, for the males can be divided
into two sets, differing greatly in the size of
their bodies and in the development of their
horns, without intermediate gradations. In a