Strategus antaeus (Drury) – immature biology

I haven’t had a successful experience with Strategus antaeus (Drury) in captivity. I found couple of males and females, I set them up in a plastic container with substrate (depth of over 6 inches), but no eggs ever found. This year, I looked up a little (a little, because there is no info available anywhere) while collecting and studied the habitat where I collected the series of specimens. Then on one day, I read somewhere that S. antaeus requires sandy soil mixtures with plant materials, like grass roots or dead grass, and such, which gave me an interesting impression because there are some Ruteline and Cetoniine species requiring the same environment.

Set up on 26 May 2018

I found two males and one female on May 12th, 2018 at Natchitoches Parish of Louisiana. My set up was similar to that I explained above the images, except no grass. Having grass sounds too messy, and I don’t like it. Instead, I added some peat moss (moss that you overlay on top of a garden or a flower pot). Moss soaked in water overnight has been squeezed before placing over the soil mixture of 2 : 1 : 1 of sand : substrate :  organic potting mix (here, I used Miracle-Gro Organic Potting Mix). I didn’t mix the moss with soil on purpose, hoping to see a female grab a piece and burrow. Such plant materials are used by females to protect eggs while laying in underground.

I found two eggs and three L1 larvae today, on August 7th, 2018 (after over 10 weeks). I believe these are quite fresh ones. I don’t know what made the female to decide to just start laying eggs, and not in couple of months ago.

DSC05598

Since it was rather a rare opportunity to find larvae and eggs of Strategus antaeus (Drury), I took some time observing them. An interesting factor of larvae is that they “crawl,” unlike many other dynastine scarab beetles. This kind of crawling can be observed from other scarab groups like Rutelinae or Melolonthinae. If the larvae crawl with its back, then usually, Cetoniinae. I haven’t seen any Dynastine larvae crawl like in the picture, and two dark colored larvae were doing the same thing. White one seems to be a very fresh one, not yet even started to feed. Two eggs found had a slight trace of larvae inside, if you take a closer look (hatched on around August 9-11th). The Size of eggs was quite surprising as they were larger than eggs of Strategus aloeus (Linnaeus) (in naked eyes), which is larger sister species, also occurring in Louisiana. A length of an egg (in the picture below, with scale bar of 2mm) is 4.66 mm long (major axis) and 3.63 mm wide (minor axis).

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Strategus aloeus – freshly hatched L1 larva

Strategus aloeus – freshly hatched L1 larva
11 October 2016.

Couple of larvae hatched out of the egg, and this particular larva has just got off of the egg. I wanted to share a microscopic image of it, here:

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I assume the cuticle layer of the end of mandibles are quite dense(?), so that is the only part dark colored whereas other parts of body are all white.

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
Pair, Dorsal and Lateral View_Final
INTRO
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 and pronotum. It is one of the largest beetle species in the US.

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

REPRODUCTION
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.

EGG CARE
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.

LARVAL CARE
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.

REFERENCES
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/
Scarabaeidae/Dynastinae/Dynastinae-Tribes/Dynastini/Dynastes/D-granti/
D_granti.html.