So just an update: I took out the soil today, applied a Fluon barrier, and reintroduced my beetles.

I had applied the Terro on 6/12, so it has been almost a month.

I took out like, maybe 1/3 of the soil total. As I was removing soil, I kept finding larvae, and I didn't want to kill them (I removed them and put them in a plastic leftover container with some soil while I was doing all this). I basically removed the top half of the soil for the deeper parts because the ants were mostly in these areas. For the more shallow parts, I still removed a good amount of it or just mixed it in. The blue death-feigning beetle larvae were generally in the more moistened parts, but I found the two biggest ones (like, the biggest I have ever seen, so they have probably been growing for a long time) in a pretty dry section of the terrarium that I never water--shallow and in the front and center.

I broke up a few of the small branches because I read the larvae need to eat wood to pupate. I have no idea if this is their wood "preference", though, lol.

So, the Fluon... I applied it around the top horizontal part where the lid rests. I also put a layer around the outside of the lid, as well as on the lid itself. I put some in the track area where the doors slide (not sure if that'll help) and some on the cord going into the light fixture. I also did this for our Japanese rat snake's enclosure, although he hasn't had an ant problem. Here is a picture of where I applied the Fluon ant barrier on the inside ledge (the coating isn't on it yet in the photo). I think the ants were coming in through here as well, and I didn't think to remove the lid and coat this part with anything. (sorry if it's sideways or a squished aspect ratio; dunno why that happens with only some of my images, but you can get the idea of where I put the barrier)




Oh, also, I did actually get a response from Terro customer service a few days after I contacted them. The person who replied to me only said that they haven't done any studies on "secondary" ingestion of the ant bait, so weren't sure how it would affect my beetles. I am hoping that, given the fact the beetles don't really dig a significant amount, and the fact that my larvae are still alive after a month, this is a good sign. I have basically removed my beetles' access to dead ants, and although I couldn't see where any of the dead ants were because they are so tiny, they should be all covered up by new soil at this time. Either the larvae don't eat dead ants, or they are unaffected by the poisoned dead ants.