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Dynastes hyllus hyllus - Pupating Question

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Hi everyone,

I am a first time owner of 9 Dynastes hyllus hyllus babies since I got them as L2s in May 2019.

3 of them have pupated (respectively in Jan, Feb, then Mar 2020). All girls, all beautiful and looking healthy. Just a few hours ago, the one that pupated in January has emerged. She did a stellar job growing up.

Here comes my question: my other 6 are still in their larval stage, lying around doing nothing. What’s going on? They turned L3 months ago, around the same time as the 3 pupated ones. The 6 of them haven’t been eating for months (over winter), just like the other 3, only that they haven’t pupated. They haven’t even made their pupal chambers yet. They are still alive as they move around every now and then. I keep all of them at around 16-23C. As I suspected that it might have something to do with the temperature, I have since turned up the heat for them, so they are consistently above 20C.

Please, if you know anything that might explain this situation, I would really love your help. Thank you so much for your support and for creating this amazing community.

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  • 3 weeks later...

Is the temperature of air surrounding larval container is the 16-32, and above 20" or the temperature of substrate is?

Try keep them cold for couple weeks and then put it back to warm location (or to your current location). Giving them a temperature shock may lure them to pupate. Each specimens has their own time frame to built pupal cells and pupate. They just may not developed enough and not ready yet. Just because they are from the same batch of eggs, does not mean they will emerge at the same time frame. :)

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What substrate do you use and do you keep them separately or together?

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On 4/14/2020 at 2:14 AM, Max said:

What substrate do you use and do you keep them separately or together?

Hi Max,

I make my own substrate from Traeger’s oak pellets, mixed in with some oyster mushroom mycelium (I make my own kinshi from the Traeger’s as well).

I keep them each in separate containers.

Since my first post, I have another girl emerge from her pupa successfully. As for the 6 larvae, they looked yellowish when I changed their substrate. Is that a good sign? Seemed sleepy and slow but healthy movements and firm bodies. Definitely a lot less active than what they used to be though. For the past few days they have been chewing on the new substrate (I put in some whole Traeger’s pellets non-fermented, to prevent moisture at the bottom of the containers; the larvae have since destroyed the pellets into pieces around them).

That said, they are still mostly inactive: just lying around, switching positions every now and then. 

Anything that I should be alarmed by or aware of? Thank you everyone.

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If larvae become quire yellow in colour and some of the larvae pupated, sometimes it is possible that substrate is not compacted enough for some larvae to build their cells. Usually I place about 5-10cm (depends on size of the beetle) of the regular garden soil at the bottom of the container then fill the rest with some regular substrate. The soil helps beetles to build strong pupation chamber. Simultaneously raising the temperature a little bit helps as well. I have also heard that is not unusual for some dynastes to add another year for no reason after their larvae reache pupation weight and size, but I do not think this was about hyllus, as they develop pretty fast. Congrats on your results. I had hyllus a few times, but always with mixed results, and no massive adults, so decided to take a break with these. It seems that my substrate is more suitable for dynastes hercules lichiy than hyllus :)  How degraded is your flake soil, is that close to black soil (completely degraded) or are there still plenty wood particles in it?

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Hey Max! Thank you so much. That makes sense. Now that I think of it, I probably did have their substrate a bit too loose. I guess the other 3 were just better at building cells! Now, I have their substrate quite tightly packed with lots of headroom. Since the latest substrate change re: above, they haven't ventured away from the bottom of their containers.

I sure hope they won't stay like this for another year!! I had my soil pretty degraded, yes, quite close to black soil. That was true for the last couple of substrate changes. The first few were not as black. But they all had oyster mycelium mixed in. No garden soil or leaves, and only up to about 20 Traeger's pellets in each container. Don't know why, but they already chewed them pellets all up! What did you use for your hercules lichiyi?

Per JKim's suggestion, I have put them in a cooler room for now. Maybe if they still don't start pre-pupating next week, I will put them back in my warmer room.

Thank you for the compliments! I am happy to say that the 2 girls that emerged have no deformities or missing limbs. They are still hiding under soil for now (I had them in artificial chambers, and now they are in their terrarium, resting under some soil). I would say they are about 55mm, although I haven't actually measured them yet.

Here are a couple pictures of:

- Mochi, my only pupa at the moment (she is quite a bit bigger than the other 2 that emerged)

- Lloyd, my biggest most sensitive baby yet, photo taken in Oct 2019 (name was given at L2, no idea still whether it's a he or she). Yellowish and bumming around as of today.

I would obviously be excited about larger-sized individuals, but it's more important to me to see them happy and healthy!



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  • 6 months later...

Lloyd pupated 2 days ago! The breeder who sold me the larvae actually told me that this species randomly chooses on its own whether to have a one or a two-year larval stage. Guess this boy just wanted to stay young for a bit longer!

As I was running out of my own pre-made substrate, I ordered some from https://www.coleopterra.com. Can attest for high quality service and product!

Length of his pupa is 105mm.

WhatsApp Image 2020-10-21 at 7.11.51 PM (1).jpeg

WhatsApp Image 2020-10-21 at 7.11.51 PM.jpeg

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  • 3 months later...

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