Beetle
The largest order of animals on earth. The ones people keep are mostly rhinoceros and stag beetles, and most of a beetle's life is spent as a grub underground.
Overview
Most of a pet beetle's life happens somewhere you cannot see it. The rhinoceros and stag beetles people keep spend 12 to 18 months as a grub in decaying wood, another 2 to 3 months as a pupa, and only then emerge as the armoured adult everyone actually wanted, which lives 8 to 12 months. That is a Hercules beetle's timetable and the shape of it holds across most of the big ones.
Males carry the horn and females do not, and the difference is not subtle: male Hercules beetles average around 34 grams against 16.3 for females. The horn is not decoration either. The muscle that works it pulls with about 140 newtons, which is roughly 14 kilograms of force out of an insect.
Temperament
Docile, slow and mostly nocturnal. A big rhinoceros beetle will sit on a hand and grip hard enough that pulling it off risks hurting it, so let it walk on and off rather than lifting it.
Males fight each other. The horn exists to lever a rival off a feeding site or away from a female, and two males in one container will use it for exactly that. House adult males separately unless you are deliberately pairing them.
Care and grooming
Adults eat rotting fruit. In the wild Hercules beetles forage for fallen fruit on the forest floor, and in captivity banana and mango both work, though beetle jelly is tidier and attracts fewer flies.
The grubs are the real husbandry job. They eat the substrate itself, so it has to be properly decayed hardwood rather than fresh sawdust or garden compost, and it needs topping up as they work through it. Damp and never wet: substrate you can squeeze without water running out of your hand.
Living and exercise
Depth beats floor space. A grub wants six inches of substrate at minimum and more for the larger species, because it feeds by burrowing through the stuff and then builds a chamber down there to pupate in.
Do not dig up a pupa. The chamber is fragile, and a beetle whose cell collapses often comes out with a bent horn or crumpled wing cases. Adults want the opposite setup: shallower, with bark to climb and something to hide under during the day.
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