The Crawler Fly is a monster appearing in ObsCure, generated by genetic mutation of Mortifilia.
This monster has the look of a giant scorpion fly but a closer inspection reveals its true and disgusting nature: the upper half of its body is made by a disproportionate human fetus that uses a mutated umbilical cord as a tentacle, while the bottom half is an equally gigantic wingless fly that is in charge of locomotion. Herbert Friedman described this kind of abomination as a "Mutation Type 4", something that happens when a contaminated subject is left in a non-sterile environment so it is likely to come into contact with insects or other small parasites, which become part of the metamorphosis mixing their characters with human ones: in layman's terms, he left some Mortifilia-infected fetuses exposed to unprotected environment, so they merged with the flies that swarmed on them.
You can see a specimen in the janitor room as he flees through an air duct after opening in two the man's body. The first encounter happens in the Cafeteria. This creature runs on the ceiling, quickly moving through the air ducts of the school and attacking with its prehensile proboscis capable of causing modest damage. His strongest attack, however, consists in grasping the prey by the neck with its tentacle and hanging it above the ground to strangulate it. If the player is grabbed by this attack it will be very hard to remove, especially if it can not count on the help of a companion.
The Mortifilia spores that wrap around the Crawler Fly, however, are not particularly durable and allow to obtain the best on the creature using a simple gun with flashlight.