I have a lot of mites in my bin. Never caused a problem. Sometimes it is a little off-putting when there is a thick layer of mites on some especially appealing food item. I had a higher population of mites back when my worm population was less, but now that I have a lot of worms all through the bin they seem less predominant.a

"Spider mites" such as the ones that cause a problem on house plants are really too small to see. There are about 50,000 species of mites in the world, but "spider mites" tend to be the kind people have heard of (all mites are arachnids). The ones that live in a worm bin are decomposers, not live-plant-eaters.

Really? I wasn't sure if they were like the bad red spider mites that kill my plants that maybe had been in the soil and went dormant when the weather got cold, only to revive when the bin came in the house and was at a near constant 70* degree temp.
I wasn't sure if they were possibly predator ones because when I found this article, the mites seemed to match the description of being the predator ones.

I was just worried because every summer I get a bad infestation of the ones that kill plants. So, I thought if I needed to kill them now then I better.

Thank you for letting me know though! Least now I don't need to worry about them hurting my worms then or the future plants when spring comes around.

"According to Walter & Proctor (1999) the highest diversity of mites occurs in soil and decaying organic matter – apparently a handful of forest soil can contain as many as 100 different species..." - taken from the article you linked to above.

I doubt they are spider mites (the kind that attack plants), because those feed on plant sap its not likely they would survive, much less, flourish in a worm bin. Add to that they are about 1/50" or half a millimeter, that's like really tiny (its hard to tell from your pictures since there is nothing of known size in them to compare against) and they are associated with webs... thus the term SPIDER mites. Your worm bin is full of creatures... if your system has matured it should be in balance thus you've got nothing to worry about.

About the fruit flies... if you cover your fruit pulp additions there shouldn't be an issue. You don't give a clue as to the environment of your bin... You don't say whether your bin is indoors or out... or what zone you live in... what you are feeding and what bedding you are using. Make sure to try and bury pulp under an inch or two of bedding... even some newspaper or cardboard should do the trick. If you are feeding rotten fruit (generally the source of fruit flies in winter in most zones) stick it into a plastic bag and then that into the freezer for a day... thaw and give to worms. Not only will that kill the incubating fruit flies but it will also cause the cell walls of the fruit to burst spilling its contents much to the delight of the bacteria and thus the worms in the bin... I'm saying it will decompose much faster.

That's good to know. Thank you!

As for the bin itself. It's an unused planter. about 2 feet deep by 1 foot wide.
Food wise, well the soil itself is a mixture of used potting soil, compost (my dad gets it from his work, a waste water district), and local dirt.
House Hold food is a mixture of coffee grounds, corn bread crumbs, some wet, soggy leaves, a few carrots, Romain lettuce scraps and within the past few days, old canned pumpkin (no mold on the contents but, around the rim of the can), and an apple.
My location is Southern CA, about 4 hours up from the Mexican border.

I haven't been able to bury the fruit with new dirt/compost since the bin is already full within a few inches to the top.
I believe the worms are doing well, when I saw a bit of mold today, I mixed up the top area and moved a few inches of soil/food remains and disturbed a few wormy residents.

My worms are, naturally found. On the days when we've had heavier rain, sometimes I'll go out into the early evening and look for any and all worms that wind up on the road or in the street gutters.

The bin/planter, is brought inside if it gets to 40 degrees or lower outside. So lately, it's brought in at night. Though sometimes it stays inside the house all day. On sunny days when there is a few hours of sunlight I'll wheel it outside and into the sun. Otherwise, the worms stay close to a constant 70 degree temp when the bin is kept inside.

Sarah... if those worms are locals from off the road then they might be "regular" earthworms (nightcrawlers) that live in burrows deep in the soil. The ones used in worm bins are those better suited to living in closed environments... meaning, that don't mind being crowded and that live on the surface of the soil albeit in and under lots of organic matter. The earthworms that you got off the road are likely the kind that are strong diggers and live in burrows deep into the earth and are mostly solitary, coming up at night to pull organic matter down into the burrows to consume... these loners typically don't do well in worm bins. You should make sure you know which type of worms you've got in your bin... ya want the ones that live among the leaf litter or in manure. These are the worms that should have nothing but organic bedding in the bin with no more than a few handfuls of soil thrown in for grit... as they are not strong diggers they need no more than a foot or two of bedding and will live happily in the organic bedding with the added benefit that they can also munch on it.

Those carrots (and any other root vegetables) you'll likely want to either grind up or freeze-and-thaw before feeding otherwise they will take a long time to decompose enough to become "food" for the worms... the other stuff you mentioned is good to go. As far as burying the food to keep the fruit flies at bay... you can wet down several sheets of newspaper or cardboard and lay it over the top and that should suffice to keep the fruit flies from breeding.

Oh dear.

Well, I'm not sure what to do then other than what would cause a major disturbance of the whole container.
Funny though, at least far as I can recall, I never see a mention of any worms being the type that hate being over crowded (at least no one making reference to them -which would be good if they did.)
I just notice a worm or two when I push back some organic matter/soil. So, I figured, ok they're near the top, they must be enjoying themselves. I've never dived deeper because I feared I would upset them with such a mass disturbance.

Should I remove several inches of soil and check on them or what should I do to see if they are happy?
What happens if they become a bit crowded? Do they start killing off some of their kind?

As for the food, well from what I can tell of these mites now they seem to break down the food quickly enough. I have no idea how one can tell if worms are being fed enough. I didn't want to over feed them or make the bin too acidic.

I became more worried though when I came across articles saying that if these mites become too abundant they will compete with the worms for food. So, I took some of the food out with the mites and set it several feet away, hoping to, alleviate a bit of their population.

For now with the fruit flies I put a bit of soil on top of the food I had. And then put a plastic bag flat on top of that with a planter pot dish on top to keep it weighed down. So hopefully that works.

Sarah.... the type of worms you really need for a successful worm bin are called "red wigglers". Though there are a few others that will work as well, red wigglers are usually the easiest ones to find and are considered by many the best ones to use in a composting worm bin. Here's a link that explains a little about it http://home.howstuffworks.com/vermicomposting1.htm

You very likely may be able to get them free in your area if you know where to look for them... try any place you find a pile of decomposing organic matter... manure piles, compost piles, etc. If you find a mass of small (compared to most other earthworms) red worms, you've likely found the right type to start your worm bin with.

Worms basically eat organic matter that's very small (their mouths are very small) and the mites (as well as other critters are what we'll just call "shredders") help to reduce larger pieces down into bit-size chunks for the worms... so I wouldn't be too concerned about the mites competing with the worms for food.

You might want to replace that plastic bag for wet newspaper or cardboard since worms actually need oxygen (they "breathe-in" oxygen through the moisture at the surface of their skin)... my thinking is that that any plastics film or sheet is going to be a barrier to gasses (including oxygen) exchange within the bedding. Also if the bacteria within the bin cannot get enough oxygen the good ones (the aerobic bacteria) will die and the bad ones (the anaerobic bacteria that produce foul sulfur odors) will begin to flourish... and many critters (remember the "shredders"?) that depend upon oxygen in your bin will also perish.

Below I've added a couple more links to one page articles describing the types of earthworms, with mentions of the red wiggler (also known as Eisenia fetida)... these short articles should give you an even better understanding of the type of worms you need to start a successful worm bin.

http://animals.mom.me/list-types-earthworms-6416.html

http://www.worm-composting-help.com/earthworm-types.html