Breeding beetles starts with keeping the larvae and adults in the correct environment; this means proper food, temperature, humidity and space for the species that you have. Breeding will start automatically once you have a male and a female in a suitable environment.
Getting a male and female
Almost all beetle species need a male and a female to reproduce, they are not parthenogenic.
Male and female beetles can be distinguished from one another by several methods. the adult beetles are the easiest to tell apart. Some species are sexually dimorphic: the male is much bigger and has antlers or enlarged jaws designed for fighting. The female does not have these antlers or has very small ones. Sometimes females have adaptations to help her bury eggs. Species that are not sexually dimorphic have some small traits that can be used to distinguish males and females. Males generally have ‘bushy’ antennae with hairs or long stalks on them, while females have much less ‘decorated’ antennae. For a keen eye with a magnifying glass you can also see the difference in genitalia and the last abdominal segment. Males have a broader last segments, while females have a last segments that is mostly covered by the second last segment.
Placing the eggs and grubs
The beetles know pretty well where they should deposit their eggs to allow them to hatch. If you have a terrarium with the correct environmental conditions it will all work out. Leave the eggs were they are and remove the larvae as soon as they hatch. Grubs that are left with eggs can start eating eggs when they do not have enough space or food. Place the grubs in a separate, suitable, container. If you want to raise a lot of beetles this is the best way to do it, but if you just want to keep beetles for fun then you can just leave the eggs and grubs in the soil of the terrarium where the adults are kept.
Some people have taken up the sport of breeding beetles that are as large as possible. Especially rhinoceros beetles are kept and bred for this purpose. If you want to have beetles that are as large as possible, keep the grubs individually in large containers and feed them a lot of food. In this way they do not have any competition for space and food among each other and will grow at their intrinsic growth rate until they reach their genetic maximum size.