I've got one of those "Giant African Millipedes" (Archispirostreptus spp.) They like it damp, with high humidity, so I think a dart cage would probably be perfect. Temps from 75-85 dF, so the temps would be okay..the only thing is, at least for the Giants, is they get big; mine is 28cm long. I feed it cucumbers, lettuce, and carrots..cricket/roach fare.

One time, he did, at least it felt like it, nibble me after he hadn't eaten for a day or two. I don't know if they'd do that to a dart, especially if you kept them well fed.

I don't know jack about smaller species, though. Did you have anything in mind?
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2.2 Corn Snakes
1.2 Leopard Geckos
1.1 Crested Geckos
1.2 Green Anoles
1.0 Russian Tortoise
3.2 House Cats
0.0.1 African Millipede

RIP
Alice, Bruno, Lars