Are you buying adult crickets? And what size is the cricket keeper? If you have flies in it, it's probably a bit humid, messy, and crowded. You might want to put them in something that allows more ventilation and only feed them as much as they'll eat.

I kept mine in a 20 gallon tank (granted, I'd go through 1,000 a week rather than 12, lol) with a screen lid. I used paper towels as the substrate. I gave them water in a plastic jar lid, with paper towels in it so they wouldn't drown, and I'd change the towel daily. I fed them fruits/veggies/greens, grains (wheat bread, healthy cereal, rat pellets), and protein (monkey chow, meat, etc). I also gave them cardboard egg cartons to hide and climb on, and I'd completely clean it out once a week.

Keep the temperature in the 70's if you can, and low humidity. Depending on what your keeper is like, they may need a better lid and/or a larger habitat. The higher the temps, the faster their metabolism, the faster they die. And the humidity in there will cause mold and attract the little flies. They may also not be getting enough water, depending on what veggies to feed them and how much they eat, and it's possible they're not eating much of the substrate.

You might also want to buy medium crickets instead of large ones, if that's what you're buying. They could already be weeks old by the time you get them and some are possibly just dying of old age. Pet store crickets generally just have a higher mortality rate anyway too. They're kept in crowded, messy, humid conditions and are bashed around a lot between the shipping and getting scooped up and dropped a lot.

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"Eagles may soar, but weasels don't get sucked into jet engines." - John Benfield

Ditto what Matt said. Humidity and overly moist conditions are the biggest killer of crickets. Also I've found that prefer to have green leafy veggies put in daily. They gobble them up and seem to live longer.

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Mike
"Never worry about numbers. Help one person at a time, and always start with the person nearest you." - Mother Teresa

What in the world are those tube things on the side? Are they for feeding the crickets without having to open the lid or something?

If you can do so without them escaping, you may even try leaving that top hatch open. But paper towels, and not leaving too much food in there should hopefully help. But most of those crickets are probably somewhat old, and came from messy and humid conditions in the store, so I'm not sure if there's a whole lot you can do. Hopefully this helps.

Oh, and you can substitute crumpled paper towel or Kleenex as something for them to climb on. They don't really like being stuck in the open with no shelter.

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"Eagles may soar, but weasels don't get sucked into jet engines." - John Benfield

The tubes are used as hiding spots for the crickets, they climb up them and then when you want to get some out you pull the tube out and tap it. That way you can get a few out at a time without everyone escaping...

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Ohhh, I see. Funky. I've never seen those before

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"Eagles may soar, but weasels don't get sucked into jet engines." - John Benfield

the tubes are actualy not that bad of an idea, but usualy its cheaper to buy a 10 gallon tank and A screen lid then what those cricket keepers go for. I use a 10 gallon tank I had lying around. You can throw old toilet paper rolls in, and it works almost as good.

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