The comparison is a matter of antiquity.
The ancient Greeks called the insect [Greek: Mantis], the divine, the prophet.

The worker in the fields is never slow in perceiving analogies; he will always generously supplement the vagueness of the facts.

He has seen, on the sun-burned herbage of the meadows, an insect of commanding appearance, drawn up in majestic attitude.

He has noticed its wide, delicate wings of green, trailing behind it like long linen veils; he has seen its fore-limbs, its arms, so to speak, raised towards to the sky in a gesture of invocation.

This was enough: popular imagination has done the rest; so that since the period of classical antiquity the bushes have been peopled with priestesses emitting oracles and nuns in prayer.
Good people, how very far astray your childlike simplicity has led you! These attitudes of prayer conceal the most atrocious habits; these supplicating arms are lethal weapons; these fingers tell no rosaries, but help to exterminate the unfortunate passer-by.