Larval stage: Beetle larvae go through a series of metamorphosis through stages called instars. Species commonly available on this and other sites including, Lucanids (stag beetles), Dynastids (Rhinoceros beetles), and Cetonids (Flower beetles), go through three instars before pupating. Species uncommon to the captive trade such as Cerambycidae (Longhorn beetles) go through many more instars, and the total number one goes through before pupation varies from specimen to specimen.
Beetle larvae from the three commonly kept families described above require a diet of flake soil or kinshi in captivity, this can be bought or made. Kinshi is often used to rear larger major males, but it is only used for stag beetle species and is not accepted by all species, so species-specific research is required if you wish to use kinshi instead of flake soil. Flake soil is more readily accepted by most species, though some species prefer dryer or more humid substrate than others. Flake soil should be changed out every one to three months of use, or when more than half of the substrate has become frass (larval feces) Though retaining some of the old substrate is required, so as to not shock the larvae’s digestive systems with entirely new substrate and possibly consequently killing them. Many species like most stag beetles are cannibalistic in their larval stage, however, most dynastids can be kept communally without issue, so species-specific research is necessary when selecting housing.
Sometime after larvae have transitioned into their final instar (generally L3), they will develop a noticeably different, yellowish, wrinkly skin that was once white or clear, this is the prepupation stage. Larvae will often dig to the bottom of the container they are housed in when they are nearing pre-pupation and form a pupal cell against the side of the container, which allows you to watch the development of the pupae. However, if this pupal cell is disturbed and ruptured it is advised to remove the prepupae and place it in an artificial cell, as many larvae aren’t capable of building a second pupal cell and will die otherwise. It is also advisable to place pupae that have been disturbed and the male pupae of large species such as Dynastes hercules hercules into artificial cells. These artificial cells can be made from various materials including wet paper towels, cardboard, and carved-out wet floral foam.
After a pupa ecloses into an adult, the freshly emerged beetle’s exoskeleton is still soft and very fragile, so handling the beetle is discouraged for the first few days. After the exoskeletan hardens, newly emerged adults go through a dormancy period often referred to as “inactive” Avoiding handling the beetle until they become active is advised, as inactive beetles are still fragile from emergence, and disturbing them in dormancy can expend needed energy resulting in a premature death. Most commonly available species dormant period is around a month, but species such as those in the Homoderus genus can have dormancy periods over 6 months.
Once your beetle has begun wandering around the container it’s being housed in regularly, it has become active. After they become active, adults require a diet of beetle jelly or non-citrus fruit. Raising the room temperature can induce faster growth and shorter dormancy periods, but this also shortens the adult life and can also result in raising smaller adults. Most hobby species should be kept from 68-78° F, with temperate and highland species sitting on the low end of that range. Ensuring there are enough objects for a beetle to be able to successfully flip itself back over is necessary to avoid premature death. Species like lucanids of the Dorcus genera are long-lived and can live over 2 years in adult stage, however, species such as those from the genus Megasoma live only a couple of months in adult stage.