with those males with the greatest ornamentation,

ensuring that their own male offspring receive the

genes for the maximum showy horns and bright

colors, and that the pageant continues.

The situation in Chalcosoma is a classic example

of sexual selection, where a characteristic with no

obvious value for survival—in fact with negative

survival cost, as it is expensive to produce in terms

of resources, and makes the bearer less agile, more

conspicuous, and at greater risk of predation—is

maintained and enhanced because its possessors

are, seemingly arbitrarily, more appropriate mates.

Sexual selection is at odds with regular natural

selection, in this case the former driving the

extreme adaptations of the male; the latter

favoring the camouflaged, secretive, unadorned

female as a better survival strategy. Parallel

situations exist with the tails of peacocks and

some pheasants, or the antlers of deer, or, some

might add, certain expensive sports cars.

The adoption of extreme structures via sexual

selection appears throughout the Coleoptera but

is most obvious in the Scarabaeoidea, and it is not

necessary to go to tropical Asia to observe this.

Stag beetles (Lucanidae) in gardens and yards in

Europe and North America demonstrate the same

effect. Not all extreme modifications result from

sexual selection. The huge, fanlike antennae of

some Elateroidea serve a practical function, to sift

the air for minute quantities of target chemicals.

The huge hind legs of some Chrysomelidae,

subfamilies Bruchinae and Sagrinae (see Sagra

buqueti, left), may serve an antipredation function,

which is still not fully understood.