Predatory beetles may need wet substrate to lay eggs in

Hisserdude

Hisserdude

Dynastes
I have been keeping 2 species of rove beetles ( Creophilus maxillosus, unknown sp. ) for about 3/4 months now, on moist coconut fiber. I have fed both species mealworms, and the occasional dog food piece. No eggs were ever laid. This week, I changed the substrate in the C.maxillosus cage, due to a grain mite outbreak. The new coconut fiber was wet, due to me being too lazy to dry it out. It was wet enough to squeeze water out of it easily. Yesterday I checked their cage and found 3/4 eggs at the bottom of the cage. I moved the eggs to their own container. That same day, i changed the substrate in the unknown sp cage, due to mites in their container as well. The new coco fiber was wet as well. Today i checked their cage, and found 3 eggs. Now that i think about it, my Harpalus penlyvanicus layed eggs in wet toilet paper in a milk cap. Maybe predatory beetles like laying eggs in wet substrate, for some reason. Does anybody have some other ground beetles they can test this out on? I am gonna try it out on my Carabus nemoralis. Who knows, maybe this could be a really big advancement in predatory beetle keeping! Or maybe it could be a fluke. Whatever it is, it could not hurt to try, lol.

 
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What do you mean "at the bottom of the cage"?

As in visible through the glass?

I will try catching/breeding the small black carabids I recently have seen running about under logs
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Yeah, they were visible through the glass at the bottom of the container. Most of the eggs have hatched now, I have 7 cute creophilus maxillosus larva! They are eating pre killed mealworms. Good luck breeding your ground beetles!
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Wow, my C.maxillosus larva are growing really fast, one is ready to pupate already, and it has only been 10 days since the first eggs were laid!

EDIT: Actually, it was just molting into a bigger larva, it was as large as an adult already so when I saw it build a cell at the bottom of it's cage I thought it was pupating. Oh well they still are growing fast!

 
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My carabus nemoralis female refuses to lay any eggs, she is really gravid looking, and she has a male in with her. I hope she lays them before she dies.

 
Perhaps toss a couple of isopod species (or any other adultproof prey insects) adults refuse to eat in there? Orin I think got C. scrutator to lay eggs with Porcellio as larval food.

Have you tried the wet substrate trick with any ground beetles successfully yet?

Also do you think eggs would be easily visible in plastic containers?

 
I will try that, I have a O.asellus in with my female, and she refuses to eat it, I may put her in my O.asellus colony, which is thriving BTW.

Unfortunately, I do not have any other carabids, I had a bunch in a small container, and made the mistake of putting two beetles with some parasitic mites in with them. The mites spread to the other ones, and the beetles grew sickly and died.

Yeah, I would be able to see the eggs, even if she did not lay them on the bottom or the side, I dig through the substrate every now and then.

I may try to give them a cool period, it might induce egg laying in the spring.

 
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What I meant was if you had used wet substrate to get eggs from ground beetles in the past. I have a suspicion that ground beetles may not lay eggs in the same conditions rove beetles do.

And I heard C.maxillosus larvae are supposed to reach maturity and pupate in about 14 days, so you are still not far off!
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I have gotten Harpalus penslyvanicus to lay eggs in wet toilet paper in a milk cap, and they layed eggs in the surrounding substrate, which was very moist.

They still are growing, they eat a ton lol!

 
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I have read scientific reports of C.maxillosus laying eggs in wet sand as well, and apparently lays more in sand than in other wet substrates
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