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Carabus Nemoralis questions - a bunch of them

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Found out a nearby facility will be putting down pesticides this friday, and their area used to be absolutely covered in carabus beetles (I've counted over 40 one night in the spring while all the worms were coming out onto the sidewalks) so I got permission to gather some.
These are my first pet insects (that weren't obtained as feeder food) so I'm not entirely positive what I'm doing. I've got a bunch of questions. Let me know if I should separate these into their appropriate forums instead, I thought that since there were so many that it would fit a bit better as a general discussion.
1) What kind of soil should I be using?
I've found two consistency choices where I've gathered the beetles; "mud"-ish/potting soil consistency, and old bark chip/potting soil consistency
2) How much space do they need?
They don't seem to wander much at all when they have easily accessable food.
3) How much digging room should I provide?
I've only seen them dig directly under objects, or maybe up to ~2cm deep, will the females end up digging deeper if they want to lay?
4) What can/cannot be in their container? Would anything potentially eat carabus eggs? A couple things were already found in the soil;
Other insects found in soil (and removed): Young isopods, Very tiny snails, small rove beetles, pot worms
Other insects known to be nearby: Huntsman, small millipedes, small centipedes, banana slugs, smaller ground beetles, mosquitos, earthworms
5) Based on the areas I've found them, they love humidity. Is there anything I can do or add into the enclosure that would prevent mold from growing?
6) Would they eat small dubia roaches?
7) Will they cannibalize? (seems easier to keep a few together so they can work together on finishing off huge earthworms)
8) Are there any food items I should never give them? (will only be offering vegetables, fruit, and insects...would anything possibly cause problems? Like citrus or onion?)
9) Are there any general "safe" foods other than carrot?
Breeding/Egg laying:
10) Would a small enclosure prevent a female from laying?
11) Are they a species that will suddenly decide not to lay (or abort) if they can't find a suitable lay site?
12) Would a female beetle act different if she is gravid or close to laying?
13) Are eggs laid one at a time, or in a cluster? (can't seem to find any pictures to get an idea of what to look for)
14) Will the beetles eat their eggs?
15) Any idea on life span?
16) Will they need to do some form of brumation?
Right now they're being kept in seperate tupperware containers, with tiny plastic hides and soil gathered from the same area that the beetles had been found. I've also gathered a couple dozen isopods from the same area, and have a few of the smaller ones in with each of the beetles to help keep down waste. They're being offered earthworms, crushed dog food (the isopods love it) and some bell pepper (which the beetles appear to love, but have issues chewing?)
I'm not entirely sure if the soil itself is very safe to use. I was told that no pesticides had been used yet, but of course there are other bugs in it. It's possible some of the bugs I've listed being around/in the soil have laid eggs in it, there are some white specks in some of the soil that looks like bits of sand.
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1) A mix of both types of soil would probably be best, if you can't do that, then just plain old potting soil will work find, (don't use any with any unnatural additives or fertilizers though!)


2) Depends on how many you have, if they are too crowded, they may turn on each other. I think you could fit 3-4 per gallon, so long as they have plenty of food.


3) 1.5-2 inches should be the substrate depth, they like to burrow a lot, and the female may not oviposit in shallow substrate.


4) Isopods should be fine, in fact, a good population of isopods may even be an egg laying impetus. Same goes for worms, which I gather are one of the the adult's favorite foods. Rove beetles, huntsmen, centipedes, and other ground beetles shouldn't be in their substrate, they would probably eat the Carabus eggs.


5) Isopods and springtails will help control mold growth, there shouldn't be too much mold growth in the substrate itself, only around dead prey items.


6) Possibly, you'll have to test what they'll eat yourself. I know they'll eat mealworms, and in the wild they usually eat worms, slugs and caterpillars, soft bodied slow moving prey.


7) As long as they have adequate room and are fed often, they shouldn't cannibalize.


8) Don't feed them any vegetables, they won't eat them. Carabids generally only eat insects, freshly dead or alive, but they do nibble on fruit too in captivity. Oranges would probably be fine, apples and bananas will be better though.


9) Don't quite know what that means, but they definitely won't touch carrots. Earthworms will probably be your go-to prey item for them.


10) Yes, probably. You'll want to give them as much space as possible, and give them a good variety of hides and areas for egg laying.


11) Yes, one of the hardest challenges in breeding Carabids in captivity is getting them to oviposit, many species just end up dying before laying eggs, even if they live for years in captivity. Seasonal queues apparently play a big role in getting ground beetles to breed.


12) A gravid female will get a lot fatter, her abdomen will extend well beyond her elytra. Other than that, she won't act much different I don't think.


13) They are laid individually, not too close together, usually near the bottom of the enclosure.


14) If not fed well, it is possible they'll resort to cannibalizing their own eggs.


15) 1-3 years is the norm for large Carabids, don't quite know how long this species I'm particular lives.


16) It'll probably play a big part in getting them to oviposit, so yeah, when it gets cold where you are, make their enclosure similarly cold.


Carabids are very difficult to breed in captivity, no one I know of has ever bred any Carabid species for multiple generations, with the exception of Anthia and certain tiger beetle species. The larvae of ground beetles often have HUGE mortality rates in captivity that are usually caused by unknown factors.


So I wouldn't get my hopes up too high if I were you, but I wouldn't give up either. Good luck with this project, keep us updated, hope they do well for you! :)

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Thanks for all the info! I saw that you made a post quite some time back about finding a possibly gravid nemoralis, did you ever manage to get her to lay?

No problem! :)


Sadly no, she and her mate died without ever producing any young, even though she was very gravid. :(

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Dang, that's a shame! I have been having trouble figuring out how to get them to lay, there are plenty of publications and research about what they eat but not much about laying behavior or preference. Kind of just trying to mimic the environment I found them in and hoping for the best.

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Dang, that's a shame! I have been having trouble figuring out how to get them to lay, there are plenty of publications and research about what they eat but not much about laying behavior or preference. Kind of just trying to mimic the environment I found them in and hoping for the best.


That's the best thing you can do really, just try to mimic the area you found them in as close as possible! :)

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