Other bug inhabitants

I stayed up late tonight and looked at my terrarium after it had been in the dark for a while. Apparently there is a lot more in there than just mantises!

my terrarium was made with a bunch of soil and plants from my garden. 

thetr are a bunch of tiny flies that look like fruit flies with SUPER long legs- legs as long as the mantis nymphs. 

Theres also a full grown slug! Like two inches long! And a couple of pill bugs!!

i've noticed that tank has a lot fewer mantises lately, do you think any of these creatures could be hurting my mantises? I am gonna give away/release most of these fellas anyway but I'll also choose some to keep and don't want my chosen few to be hurt. 

I searched long legged fly and found this: https://en.m.wikipedia.org/wiki/Dolichopodidae

dunno if that's them but it sounds like if it is, they could potentially hurt my mantises. If the mantises don't eat them tomorrow I'll remove them.

how about the slug/pillbug?

You generally want to be careful what you use to start a terrarium and what you add into it to ensure you don't introduce pests, predators, parasites, and pathogens. Usually the substrate is some sterilized mix and not something you've dug out of the yard, plants are terrarium-suitable and free of pests and hitchhikers, and any decorations have been washed and sterilized. Once you've added pests into a terrarium, they can explode in numbers as a result of isolation from their natural predators. Parasites and pathogens can accumulate over time into densities greater than what would be found in the wild, and any pets contained within will have no way to move and escape an unhealthy area.

Slugs can multiply in so high of numbers that the terrarium walls can become unsightly with slime and they can devour the plants you're trying to grow. Pillbugs and sowbugs are generally safe, but they can be opportunistic and may attack newly molted mantises if they're within reach. As for flies, there are too many species to be sure whether or not they'll be detrimental and although we know many species are parasitic, their life cycles are poorly studied.

Pillbugs are sold as tank cleaners and are 100% fine with mantids, and can become a snack for adult mantids too.

The slug though could inadvertently be harming the nymphs, as the slime could easily trap/kill the tiny nymphs. Also as it seems everything is from your yard that has not be baked/boiled/microwaved, there are likely centipedes or spiders in there as well, and making a snack of the nymphs.

You really should remove your remaining nymphs from that tank, to a clean container, as it is hard to say what is all in there with them (and escaped/ing into your room as well from it).

They gave good advice, I would hurry if I were you t o follow it.

Thanks everyone. 

Yeah I really don't know what's in there. Initially that seemed like a fun adventure but now it's more scary. I've already had so many nymph deaths from various causes.

i'm gonna redo that terrarium without the unsteralized materials and I'll also prolly put a divider in so it can hold multiple older mantises without them being able to get at eachother

Keeping mantids readily visible to each other in that style enclosure can keep them stressed at each other. Always threat displaying.