The Book Flie is found in the dry and dusty places, like withered trees, old houses, and libraries. The Book Fly is a large, fetid fly with a blue shine. It has an annoying bite which is harmless but draws some blood. However, during mating season, the fly swells up with slimy eggs glittering under its belly. It will attempt to lay these in any dry wood it comes across. Books are especially attractive. The eggs have a two week gestation period, during which they will become larvae and start devouring the wood. After this period the flies will be fully grown and take to the air. The flies are considered a pest, if a library or ancient building has one case of these flies, more will surely follow. More than once has a scholar opened an ancient tome with a shriek as a cloud of young Book Flies buzz forth from the invaluable document. There have been reports of entire cities loosing their written history and all things paper because of an infestation of Book Flies.
Wind Flies are small and slender insects with long antennae and finely veined wings. They nest in large colonies in humid forest caves and are victims of many legends due to their patterned life cycles. When a member of this fly species has finished its life cycle it will find its way back to the cave where it was born. There it will breed and lay its eggs. The number of flies that breed in one cave can number hundreds of thousands. The curious thing about this is that when the young brood are ready to take to the air, they do it together. Vast clouds of buzzing flies rise up from the forest roof, they connect their tiny feet together and form a web sailing on the wind for vast distances. When this web finally breaks the flies descend on the land below to live their lives, and later repeat the cycle.
These nocturnal flies are considered a bad omen and are believed to be connected, somehow, with the world of the dead. They are of a bright brown hue, with a black warts along their backs, and their multifaceted eyes are of a dull red with tiny whitish spots. Their lifecycle is unknown, but they are reported to live inside the mouth of a species of large toads. They have piercing-sucking mouthparts and feed on blood and nectar both. Being bitten by a Omen Fly is actually quite harmless, but superstition states that this is a dark and foreboding sign that the one bitten shall soon die. The most horrible aspect of these ghastly flies, and the reason behind their name is that they sense the spirits of the dead. They are drawn to ghosts like bees to honey, buzzing in areas where ghostly shades are shambling, making them visible by filling up their invisible shape. Men have gone mad from seeing the shambling form of a man that is not there, his invisible form filled by thousands of warty, buzzing flies.
Cave Lurkers are a subterranean species of fly that in many ways resemble a spider with wings. They live and nest in deep mountain caves. They are large, milky brown and slightly transparent. Cave Lurkers make silky white webs, these webs are used to nest and to catch small underground prey like rats, bats and worms. They sometimes catch small game from the surface world that have somehow got lost in their caves, searching for a place to hide or live. Cave Lurkers form colonies, when something is trapped in their web they simultaniously spring forth from cracks in the wall and devour the prey. The cissorlike cutting blades in their mouths both tear and pierce a victim's flesh in addition to injecting an intoxicating venom. They are not flight-less, but they rarely use their wings except during mating season. There is a rumour of a vast complex of Cave Lurker Flies colonies deep down in the earth that are so big that their webs could even pose a threat to grown men.
Nasty and vile, certain to add more life to the slums and foul depths of the world. After running into a few of these varities most characters will pay careful attention the casual description of flies buzzing about the manure cart or decaying corpse.