In his book, Childhood's End, the Overlord Karellen, the "Supervisor for Earth," (Extraterrestrial/Space Brother) periodically meets with Rikki Stormgren, the Secretary-General of the United Nations. Karellen tells Stormgren that the Overlords will reveal themselves in 50 years, when humanity will have become used to their presence. When the Overlords finally reveal their appearance, they resemble the traditional Christian images of demons, particularly the goat-headed demon Baphomet, with cloven hooves, leathery wings, horns, and barbed tails.
Instead of a Baphomet creature, they report seeing a very tall praying mantis-looking alien. And oddly enough, this mantis-like being is often wearing a hooded robe.