I see you mention these flies are black, which makes me wonder if they are Fungus Gnats. Fungus Gnats are a fairly common flying insect, particuliarly in Florida and other areas which do not experience hard freezing temperatures. Typically, their larvae feed upon fungus which grows on or in soil which never dries out, and pose no risk to plant health. However, they are also known to come from another source: Sewer lines. Within most plumbing circumstances, there is an S shaped trap which holds some water in the drain line from a shower, sink, or other water "feature" within one's home. However, if this feature does not have water running through it for some time (such as a guestroom bathroom), then the water can evaporate, leaving a direct air passage to the room from the sewer lines. Often, these gnats make their way into homes through this avenue. They are then attracted to whatever source has the scent most like their original habitat, so as a pet owner, I'm sure you can imagine the rest. Hence, they appear in the reptile room. Simply running water through the drainage hole will close off the passage. Doing so regularly is adviseable.
To further expand upon this, and having worked in the professional nursery trade for over two decades, I have learned that many flying predatory species of flies adore the color yellow. Bright yellow. Typically, any plant under stress (with weakened 'immune system') will have yellow foliage (with, of course, the obvious exceptions of yellow/lutea variegates and cultivars which wholly express the lutea trait). So yellow = easy meal. Some of the organic nurseries which are certified have developed non-toxic (pesticide free) means of combatting potentially damaging insects through applying a sticky coating comprising of a mixture of glue and honey to yellow cardboard, construction paper, etc- the color yellow is the attractant. Old fashioned fly-paper was yellow for a reason. Regrettably, I cannot remember specifically which slow-to-non-drying glue or adhesive was employed for this method. If I have the chance, I will inquire a bit further.
Hope this helps.
-dave