i know what these guys are because i had them also and have done a lot of reading up on them.they are most likly fungus knats.they are attracted to the water/humidity and lay eggs in the substrate.the larva hatch and eat decaying material and plamt roots.if you have no live plants to worry about,i wouldnt worry too much.if there are no live plants they wont stick around long and will cycle out pretty soon.the best bet short of pesticides,if they do stick around,would be to let the substrate dry out completely.your snake will be able to handle this for a couple days as long as hes not shedding.you can even mist your snake a bit as long as its not enough to drip onto the floor and re-wet your substrate(it must dry out completely for 4-5 days)now they may not be fungus knats ,but another type of knat i also experienced once.they are called phorid flies.these guys are a bit tougher but still as long as there are no live plants and you dont leave feces on the floor,they also shouldnt stick around.the problem with the phorid flies is,if they begin to breed in your house,they quickly move into the drains(their favorite breeding place)and its hard to get rid of them if they do that.they can breed and feed on the protine slime that lines the walls of bathtub and sink drains.these flies,if youre a breeder,must be eliminated at any cost(pesticides whatever)because they commonly will infest and lay their eggs on snake eggs and the larve can burrow into live eggs and kill entire clutches.they are very small and can find ways into incubators .they are dirty(also called filth flies)and can spread disease and infection.the way to tell the difference is,fungus knats are super small(almost hard to see)and fly in fast,jerky motions.the phorid flies are quite a bit larger and look exactly like fruit flies except they have black eyes.they also perch with both back wingsfolded together to apear as one wing(as opposed to common flies where you can clearly see both wings when standing still)either way,they are not a big deal as long as you have no live plants(they can cause root rot and kill entire vivariums)and as long as you have no live eggs ,and as long as they dont begin breeding in the drains.another consideration would be if you have house plants,you can get rid of the fungus knats in your vivarium by drying out the soil,but if they are living in your house plants,they will keep reinfecting.anyway,i hope this helps a little.they really do suck.i have noticed this happening with those exoterra vivariums a lot.they are enclosed enough to keep humidity up,have a recess on the bottom to hold stangnent water,but also have large cracks around the doors to let in all sorts of pests.just a few reasons why i wont use them.if you do decide to keep them,try sealing off the wide cracks to keep them out.