Can be kept in small containers, if no breeding is required. If you keep your beetles in small containers, better to keep them individually or at least in pairs, male and female. The aggressive males will kill other males and the same thing may happen with females: aggressive females may kill other females in a very small enclosure. For big groups it is better to keep them in large containers with lots of hiding places created by placing pieces of wood or bark on the top of the soil. The beetles spend most of the day time hiding underground, and often become more active in low light conditions. They will escape if they have a chance, so the box should be kept tightly closed, and a few pen-size holes need to be provided in the lid or the top part in the side of the container for better air circulation.
They feed well on banana or other ripe sweet fruits or beetle jelly. They seem to like banana more, perhaps due to a high protein content. Some breeders believe that adults of these species require a lots of protein and add some yogurt into the mashed banana. I feed them with my home-made beetle jelly (http://beetlesaspets.blogspot.co.uk/2013/11/jelly-for-tropical-beetles-at-home.html).
Initially I had a massive issue with mating my first rainbows. They were placed into a properly organised large container designed for egg laying and after six months of waiting I discovered no eggs:(. After several discussions on forums I came to the conclusion that the major male (with massive horns), could not simply catch the females which were normally hiding underground. The solution was to place them in a small enclosure with no hiding places and provide food in one spot. Male normally feeds and guards the food at the same time, so catching hungry female for him was not a problem in the small box. Egg laying setup is pretty much the same as for many stag beetles: decayed oak or beech log partially buried into garden soil or mulched wood. The female burrows the hole inside of the log and deposits eggs, simultaneously filling the hole with mulched wood and with parts of the substrate. If mulched wood or fermented flakes are used to fill the box, the female may lay eggs in the substrate too, normally in the bottom layer. If there is more than one female in the container, they may clean up each others holes to lays their own eggs. After about 3 months logs are carefully split with a knife or a screwdriver and the larvae are removed. Eggs can also be removed and placed in the tubs filled with the larvae substrate.
Mulched white rotten oak will be sufficient to produce minor healthy adults. However, to grow major adults, good quality fermented wood or even better, kinshi substrate, are required. I found the procedure making kinshi a bit disappointing, as every 3rd tub I made with kinshi was contaminated, and the procedure itself was rather time- and resource-consuming. Some hobbyists use dog food as a supplement to grow bigger larvae, but I did not like this approach, as it attracts parasitic mites. In the late L3 stage the larvae will create the pupal chamber and transform to the pupa. I found that the rate of survival of the pupa is much higher if pupa is transferred into the artificial pupa container, which I normally make from floral foam. After beetles come out of the pupa, they will stay in their cells inactive for a couple of weeks and then they will be ready to mate again.
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