JKim's Collections

A Rearing Guide to the Dynastes grantii Horn, 1870 (Coleoptera: Scarabaeidae: Dynastinae)

A Rearing Guide to the Dynastes grantii Horn, 1870 (Coleoptera: Scarabaeidae: Dynastinae)

Dynastes grantii Horn, 1870
Western Hercules Beetles are found in western US states of Arizona and adjacent states. It is white or nearly white colored overall with dark spots over the elytra. It is one of the largest beetle species in the US.

Eggs, L1, L2, L3, Pupae, then Adult. Egg to adult cycle takes 12 months to 15 months depending on rearing environment.

Reproduction of Western Hercules Beetles are very easy. A pair of a male and a female or trio of a male with two females in a rearing container is recommended. Firstly, obtain a large plastic container for the rearing purpose, that is at least 20-30 cm deep with an area of around 15 X 20-30 cm. Pour in pre-moisturized substrate with large pieces or using an organic potting mix from garden store to fill up the rearing container up to 15 to 25cm, depending the depth of the container. Leaving about 5 to 7 cm at top is fine, since they do not need aerial spaces that much for their activity, unless you want them to fly around freely (which may injure them, since the container has space limitation). Feed insect jelly or overripen fruits such as bananas. Place male over female to mate them. They usually mate right away if collected outdoor, or may need some time if larvae were captivated to become fully to adulthood. After witnessing two to three times of mate, take the male out of the container to avoid any unnecessary stresses to females.

Caring eggs are quite important to rear and breed the Western Hercules Beetles, as the species spends a lot more time as an egg than any other species under a subfamily Dynastinae. Egg may take from two to three weeks up to three full months depending on its rearing environment. In a good humid environment, their time spending as an egg is quite shorter than exposed and dried conditions. Since they take time to hatch, it is better to keep the eggs in the container as laid itself, and just moving the female to other prepared rearing container is a lot easier and safer to keep the eggs all hatched in later time. Therefore, using a sterilized substrate or an organic potting mix is very important. It is easy to sterilize as you only have to moisturize it and microwave it for four to five minutes is all you need (be careful with microwave as it can burn the substrate or may cause malfunction to the microwave). Cool down the substrate, and keep the eggs in the substrate. After one to two weeks moving a female to other container, you can open up the first container to find eggs and larvae. If they are still in egg, you can replace them in a sterilized substrate in a small container so you can use the rearing container be prepared for the next round after the second container.

There isn’t much difference from other species to taking care of the larvae. All they do is feed on substrate, so only thing you need is to keep the larvae feed on a good substrate, and make sure there isn’t any other pests. They may take up to 12 months or more to pupate and emerge out.

Horn, G.H. 1870. Contributions to the coleopterology of the United States. Transactions of the American Entomological Society, 3: 69-97.
Moore, M.R. 2006. Dynastes grantii Horn, 1870. Retrieved October 19, 2015, from: http://museum.unl.edu/research/entomology/Guide/Scarabaeoidea/

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