D&D Monsters: Stirges

The strige is a creature of Roman myth, derived from the earlier Greek strix. It was said to be a nocturnal bird, albeit one that hung upside down like a bat, which drank the blood of infants and possibly even ate the remains. The Greek version of the name has since been adopted as a scientific name for a genus of owl, and, blood-drinking aside, the general description does seem to match owls more than anything else that might exist in the real world. The name later also became associated with witches and with a more humanoid form of vampire, the strigoi. 

In D&D, of course, the name mutates again to the form "stirge". While it looks even less owl-like than the mythic creature, it's still clearly based on it... but is more inclined to attack adults than babies.

D&D Monsters: Manticores

Manticores are creature not of Greek, but of Persian, myth. The name literally means "man-eater", and it's at least possible that it originated with a "traveller's tale" style exaggeration of man-eating tigers. They were supposed to be hungry for human flesh - something retained in D&D - and were often described as having a "scorpion-like" tail, although most historical illustrations show a cluster of spikes on the end of the tail instead.

When the creature was adopted for D&D, however, Gygax made a major innovation to the mythic creature: he gave it wings. (At least, this is true by the 1E Monster Manual; the original version of the rules apparently doesn't mention the feature). Although this is original to the game, it has become a common trope of manticore pictures since, even outside of D&D, although it's far from universal.