Mythology: Malay Folklore
Size: Tiny, the size of a locust, the Apocalypse Locust is Medium or Large, depending on the victim
Environment: Mostly the Abyss, but they can appear anywhere
In Mythika: Nasty little parasite bugs that appear as locusts with a human-like face, which enter humanoid victims and terrorize their bodies from within, finally merging with them into a demonic horror called a Apocalypse Locust.
Pelesit are creations of the Horseman of Famine, and indeed swarms of Locust are known to trip lands of food in an alarming rate, but the horseman also saw other use in them, taking advantage of their small size. When inside a victim the Pelesit tortures the victim for months to come, first taking care of their vocabulary abilities so they can’t scream or ask for help anymore, then creating stomach pain so they can control the victim to do their biddings, until at last the victim succumbs to the Pelesit and surrenders its body to the horrifying insects so they can merge in soul and mind, turning into a demonic mix of humanoid and locust.
Apocalypse Locusts (second picture) are powerful demons that serve only their master the Horseman of Famine, they travel in small clusters and cause famine and other problems wherever they go, often surrounded by swarms of tiny Pelesits.
Link: https://en.wikipedia.org/wiki/Pelesit
NOTE: Couldn’t find a better Pelesit picture, but that is far from what they look like in Mythika, their face isn’t female, more like a horrifying visage of a human without eyes.