30-04-15

Caresheet Dynastinae

Caresheet Dynastinae (by Tom Schouteet)

 

This caresheet represents a good guide for the breeding of the most general species of giant rhinoceros beetles of the subfamily Dynastinae (Dynastes hercules ssp., Megasoma sp.) even though slight changes should be taken into account for some species (Chalcosoma sp.). It is also adequate for smaller species of Dynastinae (Dynastes sp., Allomyrrhina (Trypoxylus)sp., Xylotrupes sp., Oryctes sp., …), but here the dimensions may be changed (size of the rearing boxes, amount of substrate provided…).

 

Stadia + duration

 

Egg: 1 to 2 months

L1: approx. 1 to 2 months

L2: approx. 2 months

L3: 12 to 36 months (for Dynastes hercules ssp. - Megasoma sp. resp.)

Wandering + prepupal phase: approx. 1 month

Pupa:  2 months

Imago (adult): dormant phase (diapause + maturation of the reproductive organs) (1 to 1,5 months) + active phase (4 to 12+ months)

 

Small species usually tend to complete the cycle more rapidly, but they also consume the substrate/food much quicker (a more regular substrate change should be conducted, every month instead of every 1,5 months for the given dimensions in the chapter “Breeding”).

 

Preparation

 

Substrate for the larvae

 

L1 - L2 larvae need the following composition for their substrate:

-          1/3 finely shredded soft white/brownish rotten wood (wood that is easily to be cracked by hand); in order of preference/quality: oak, beech, maple, chestnut, abele, poplar… No resinous wood nor needles (pine trees) should be applied (larval won’t die of it, but they won’t eat it either)

-          2/3 leaf humus (finely shredded rotten leaves or the humus mulch, the layer of fine material located right underneath the top layer of whole brown leaves)

 

L3 larvae however do feed more on the white/brownish rotten wood; that’s why the ratio here should be increased to 1 : 1 (50 % each) + preferentially have the wood layer on the bottom of each container (the L3 larvae will mainly feed on the wood).

 

Eggs are to be kept in very fine and moderately humidified leaf humus substrate (never too wet in order to avoid mold).

 

A good trick for determining the right humidity of the substrate for eggs as well as for the larvae is to grab an amount of substrate in your hand and squeeze it tightly; if the substrate clots upon opening your hand without any water running down from it, the humidity is optimal. Moreover, fresh substrate from the wood should first be acclimatized in the breeding room before being applied to the breeding boxes.

 

Local forest Brussels.JPG

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Typical oak/beech forest, very adequate for finding leaf substrate and white/brownish rotten wood (leaf humus can be found right underneath the top layer of whole decaying brown leaves; it is only a few cm thick but you can easily scrape it together). Wood can be found as logs/big branches on the forest floor

 

Adequate and humidified leaf humus.JPG

Moderately humidified leaf humus ready for use

 

 

 

 

 

 

 

 

 

 

 

Finely shredded humidified white rotten wood.JPG

Finely shredded and moderately humidified white/brownish rotten oak/beech wood ready for use

 

 

Breeding containers

 

Most types of plastic transparent containers are adequate for breeding Dynastinae larvae. Personally, I use different types of plastic boxes/buckets from the brands of Ikea (Sämla series), Braplast 5 L. boxes and Joker 6 L. and 10 L. buckets (with cover lids of course). It is also very important to make a few air holes on the side of each container (only a few are enough; the aeration must be there, but may not decrease the humidity level).

 

Temperature

 

The optimal breeding temperature for most Dynastinae hovers around 21 - 23°C, but the range is between 18°C and 25°C for some species.

 

Breeding

 

Eggs are kept in a closed box (few air holes!) with fine and moderately humidified leafhumus substrate. The incubation of the eggs usually takes around 1,5 months, so it is best to start looking for the L1 larvae after around 2 months.

 

L1 – L2 larvae are kept in closed containers (few air holes!) with a mix of finely shredded white/brownish rotten wood and leaf humus (1:3 ratio). This substrate may be entirely mixed to get a homogenous substrate for the larvae to feed on (L1 - L2 larvae usually feed on a wide array of substrate components). 1 L. of substrate suffices for each larva, so it is ok to keep up to 10 L1 - L2 larvae in a box with 10 L. of substrate; hereby, the substrate needs to be changed one time each month for these two first larval instar stages (during the substrate change it is very important to keep at least 1/3 to ¼ of the original substrate in order not to disrupt the microbiological balance in which the larvae feed, i. e. never change the substrate entirely!). After around 3 months, the fat L2 larvae will construct “pseudopupal chambers” in which they will molt to the third larval instar stage L3.

 

Young L3 larvae (< 50 – 60 g larval weight) are best to be kept separately in at least 5 L. boxes (in order to obtain the best breeding results in terms of adult beetle size). Progressed male L3 larvae (> 60 – 70 g larval weight) are best to be transferred to even bigger containers/buckets of around 7 L. – 10 L. for maximal growth achievement. Female L3 larvae never reach more than 70 – 80 g and may reside in 5 L. boxes for their entire larval cycle (they also don’t need as much space as the male L3 larvae to pupate).

 

On the other hand, if one wants to continue breeding with these beetles, it is best to at least keep one female and one male L3 larva (from approx. the same age) together in one big breeding box (usually 10 L. boxes are fine for a L3 couple or 15 L. for a L3 trio).

 

With these given dimensions, substrate change should be done every 1,5 months, in which at least 2/3 of the old substrate is discarded (preferentially the part with the highest amount of larval fecal pellets) and new substrate is added. Again, never change the entire substrate since the microbiological balance within the substrate needs to be kept for optimal larval feeding (therefore, keep at least 1/3 to ¼ of the old substrate, preferentially the part with the lowest amount of larval fecal pellets).

 

Hereby I personally advise to apply the finely shredded white/brownish rotten wood layer on the bottom of each container/buckets for at least 8 to 10 cm, top it with some fresh leaf humus substrate (a little of the old larval substrate may be mixed in) for the next 5 – 10 cm and top this layer with some of the old larval substrate (from the same larva of course!). Concerning substrate depth, this should be arbitrarily at least 3 – 4 times the biggest width of the larva, but I usually take around 14 – 15 cm for L1-L2 larvae and at least 18 – 20 cm for L3 larvae.

 

Boxes and buckets with larvae with layered substrate.jpg

Examples of boxes/buckets perfectly fit for beetle larvae. Please notice the substrate depth and the shredded white/brownish rotten wood part on the bottom of the boxes/buckets

 

 

 

After 12 up to 36 months (Dynastes hercules ssp. take around 12 (for females) to 18 (for males) months for completing their larval cycle, Megasoma sp. 24 up to 36 months for both sexes, depending on which species of Megasoma sp.) the big L3 larvae will show a darker yellowish color on their skin and this will slowly trigger them to start their wandering phase (prepupal phase) in which the larvae will be looking for an adequate location in the breeding box to construct their pupal cell. This phase can be noticed as soon as the larvae start crawling around in and out of the substrate and the substrate surface on the top of the boxes shows a very irregular shape (some larvae will even pile the substrate up to one side of the box). From that point onwards, substrate change should not be done anymore and the larva should be left alone for the whole duration of the pupal period; she will subsequently start building her pupal cell in the “rearranged substrate” (this is noticeable as some kind of “window” through the bottom of the transparent box). After finishing her pupal cell, the larva will become immobile and start the pupation phase: after 2-3 weeks it will pupate and remain as a pupa for the next 2 months in this pupal cell. After hatching as an adult beetle from the pupa, the adult beetle will still need 1 - 1,5 months more before emerging actively on the surface of the substrate (it takes a diapause/stasis period in order to have its reproductive organs matured before being able to reproduce).

 

Adult beetles, once active, mainly feed on banana or beetle jelly (apple chunks are also ok, but less nutritive). Female adult beetles are best fed for the first 2 – 3 weeks separately before being mated with male adult beetles (males however can already mate only a few days after “activation”).

 

For breeding with the adult beetles, it is recommended to have a large breeding container (at least a volume of 20 L. for one adult couple or 50 L. for a trio) filled with at least 25 cm of fine and moderately humidified leaf humus substrate (first 20 cm of very compacted/pressed substrate topped with 5 cm of loose substrate).

Breeding box 20 L. for adult pair.JPG

Breeding box 20 L. for adult pair 2.JPG

A good example of an adult beetle breeding box for one active fertilized female (the lid has been taken off for the photographs). Substrate depth here is 22 cm with highly compacted moderately humidified fine leaf humus substrate. Little wooden logs prevent the female from tipping over.

 

The female usually starts laying eggs around 1 – 2 weeks after being mated (the male may then be separated from the female in order to allow her to start digging and laying eggs in the compacted substrate, but only when one is 100% sure that mating occurred; only one mating suffices for the female to continue laying eggs for the rest of her life).

 

Around 2 months later, it is possible to already start carefully searching for the eggs or early L1 larvae in the substrate (usually the eggs are located in large compacted chunks of substrate). Of course, it is also possible to just wait for 3 months and then only find L1 larvae (maybe even some early L2 larvae already).

 

After that point, the larval cycle starts again.

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