It is a much more probable view that the rattlesnake uses its rattle, the cobra expands its frill and the puff-adder swells while hissing so loudly and harshly, in order to alarm the many birds and beasts which are known to attack even the most venomous species.

Snakes act on the same principle which makes the hen ruffle her feathers and expand her wings when a dog approaches her chickens.

But I have not space here to enlarge on the many ways by which animals endeavour to frighten away their enemies.
Natural selection will never produce in a being any structure more injurious than beneficial to that being, for natural selection acts solely by and for the good of each.

No organ will be formed, as Paley has remarked, for the purpose of causing pain or for doing an injury to its possessor.

If a fair balance be struck between the good and evil caused by each part, each will be found on the whole advantageous.