I discribe here how I did to breed flower beetles. This is maybe not the best way to keep them, but I had some good results.
Ok, lets start with those pretty worms!
The compost
If you get good compost, you are almost sure that your larvae will become adult. it's important because compost is simply the larvae food. I think that if a species is difficult to keep, it's because it need a more specific compost, and an easy species accepts different kinds.
What I used with best results (faster growing, bigger adults, more prolific) for ALL beetles I described just before, was a leaf mould found in a place where water stayed in the winter, and got away in spring. It was black in color, and there was thicks layers of rotten leaves (oak, beech mainly) in decompostition. This wasn't eaten by earthworms because of the water. Dont worry if it smells a little, the larvae love it ! remember they like rotten things, they have a good stomach.
Sometime I gathered it even when very wet, and this was not a problem for larvae. Just leave some ventilation in the larvas box, to avoid over humidiy.
I could find in other places other leaf moulds, brown, more dry, and without smelling. For exemple at the bottom of a big oak or where lots of leaves are droped. It's good too, but larvae didnt show so much enthusiasm. But this one is maybe easier to find.
You can see if the mould is apreciated : it will get transformed to small craps very quickly. (dont worry these craps won't smell more than the compost !)
What I did to increase the nutrition content of the mould was to add some comercial compost for flowers or garden. (beware of inscticids or chemical products).You can add some rotten wood (if possible oak, but others will fit too except conifer). It's apreciated to. But never give only rotten wood.
When I gave only comercial compost, it was ok but they grow not very fast and they stayed quite small. But when I gave only those rotten black leaves, I always had good results. Mixing with others moulds and rotten wood was good, also to save the precious black leaf mould.
Now about the larvae themselves.
when they hatch (in the compost the adults burried the eggs), the larvae are very fragile. It's important that they are separated from other bigger larvae or even adults. One day, I surprised an adult with a baby larva in the mouth. I could hardly believe it, and since then I always separated eggs from adults. Or I took away the adults, to leave the eggs in the original compost. this is better than taking the eggs to put them somewhere else. Eggs are small (2-3mm diameter) and it's easy to forget some.
Canibalism between larvae can happen sometimes. expectially when the mould is not very good or already transformed in craps. You can avoid this by increasing the dimensions of the box, or even separate each larvae if it's a rare species. I had this problem with Chelorrhina polyphemus. But it was ok with a 20cm rottenblackleaves/compost/rottenwood layer, in a 40X50X40cm box for about 15 larvs. But during the time they eat a lot, I had to change the compost after 3 weeks.
Changing the compost frequently is important too. ok, maybe most larvae won't die if the mould is not changed enough, but they will stay smaller and grow slowly. Past the first or second skin, they are quite strong and healthy compared to phasmids or mantids. They can survive a long period almost without food. They will simply grow slower and become small adults, with small horns for those who have one.
The nymphs
After a period of 2 - 6 month, the larvae are ready for the metamorphosis. They will build their cocoon with saliva and mould. there is not so much things we can do there, just wait. And try too keep a contsant humidity, if possible about the same that when they did the cocoon. And wait 2-3 months.
Adults
Normally, they'll
go out by themself from the cocoon. If humidity was missing during a long
time, and the cocoon looks very dry, it could be better to open it a little,
because humidity leave the the cocoon soft enough for the baby adults to
break them.
Now these babies are still fragile, and they will want to burry themself
1 or 2 weeks in the mould.
After that, they are strong beautiful beetles. Now they will need Heat and again compost to lay eggs and stay hidden in it. A thick layer of mould (the same that I used for larvae) will let the females choose an ideal place for the eggs. An aquarium will fit well, if possiple with a light to increase temperature (this will stimulate them, and make them going out of the mould for eating and mating). But the light is not necessary if the room is warm enough (more than 25 deg. C).
For the food,
I used often bananas. They like sweet things, and even overripe fruits.
Pollen will be apreciated too.
The eggs are laid in the compost, and abandonned. it better to leave the
eggs alone, and not touching them. Since adults can be a threat for them
and for small baby larvae, it's better to take them (the adults) out of
the aquarium and install them in another aquarium. This will let the eggs
hatch in peace. When the small larvae are a little bigger, it's easy to
take them in another box, only for larvae, and sort them by size if possible.
then the aquarium is available for adults again. 2 or 3 weeks in each aquarium
is ok.
About rhino beetles
just some words about those beauties like Dynastes, Megasoma, or Golopha.
Keeping these coleoptera is very similar to flower beetles. the 2 main differences are :
