Monday, 20 January 2014

The European rhinoceros beetle, oryctes nasicornis breeding report

Last spring I obtained some L3 larvae of the European rhinoceros beetle, oryctes nasicornis.  These beetles are fairly large and can grow up to 4 cm or even bigger for some subspecies such as oryctes nasicornis grypus.  In nature their larvae live in rotten wood and their distribution is often associated with compost heaps and sawdust mills.  Moreover, the relatively higher temperature during winter in compost and sawdust heaps allowed these beetles to spread far north in Europe and Asia.  Remarkably, the oryctes nasicornis is absent in the United Kingdom and has not been reported breeding in the wild in this country.  The larvae feed mainly on decayed wood, but any decayed vegetation, like the one that can be found in compost heaps, can serve as a food source. The adult beetles do not feed, however, can live several month using reserves accumulated during the larval part of the life cycle of the  beetle.

My larvae were in late L3 when I obtained them, so they turned into the pupa pretty soon. Interestingly, the pupal stage lasted only 2-3 weeks, perhaps because the containers were kept with my tropical beetles, and the temperature there was around 22-25C.  Adults (2 males+2 females) were transferred into an egg laying container (40l plastic box) where they stayed inactive for about 5-7 weeks. The egg laying container was set up as follows. Bottom layer- 15-20 cm of the garden soil mixed with mulched oak leaves and rotten wood (oak, poplar, willow). The proportion of wood:leaves:soil=80%:10%:10%. This layer was pressed hard. On the top of this layer, I placed another layer (about 15 cm) of the soil with the higher contents of mulched wood and leaves. All was finished up with individual chunks of well-decayed wood, bark and oak leaves on the top.  

The adults spent about 3-4 months inactive in the garden shed. After that I transferred them into my beetle breeding cupboard where they stayed inactive for another couple weeks.   After one night I discovered that big chunk of softwood was split into a few pieces, which suggested that something is going on there:)  I waited patiently for about two months and then checked the content of the box.  Firstly I found one female dead :( and then a reasonably big L1 larvae in a top layer. When I started digging further I found quite a few (40+:) L1s and eggs.  Eggs and smallish L1 larvae were in clumps of substrate about the size of a large cherry that was tightly packed by the female during oviposition, so it was not very difficult finding them :)  Some clumps had not just one larvae/eggs inside (please see photos below). I was surprised how big the egg of this rhinoceros beetle is; the fresh laid egg was about 3-4 mm long which then expand to about 5 mm ball. The remaining female was placed into another smallish container, hopefully she will lay a few more eggs.

Left: substrate clump (2.5 cm size) with L1 larvae ; center and right- two newly hatched L1 larvae discovered in the clump:)

From left to right: freshly laid egg, egg that about to hatch, newly hatched L1, and older L1. Same head size confirms that bigger larva is still in L1 stage. 

You can also contact me via regarding any related issue and availability of beetles.

Sunday, 12 January 2014

Prosopocoilus bison breeding report

I recently obtained a few of these beautiful beetles, so I tried to breed them. The male can reach 60 mm, females are smaller (see photo below). Just a few observations which you may find helpful. As for food they were feeding well on the home-made jelly for stag beetles, that I use for all my beetles. You can find this recipe in the topic below. (  They also seem to prefer the jelly to ripe fruits, such as grape, banana or sweet clementine.  They stayed active at temperatures between 19-25C. I kept a male together with the females;  the male was not aggressive towards the females. The interesting thing about these beetles, is that they regularly played dead when I opened the beetle enclosure and they could stay like that for minutes, and often upside down:) So you have to be very careful not to "discard" the live beetle, thinking that it has died. As an egg laying substrate I used decayed softwood chunks and logs from various deciduous trees. The females of prosopocoilus bison seemed to prefer a softer wood for the egg-laying, much softer than one which is preferred by the females of rainbow stag beetles (phalacrognathus muelleri). 

Prosopocoilus bison  pair;
male left, female right.

Few pieces of bark were also  placed in the enclosure as hiding places for the male.  Interestingly, females did not do much wood boring: the eggs were deposited into small gaps and holes close to the surface of the wood chunks. I observed female depositing eggs in a container with clear plastic sides. Female made a shallow hole/"incision" in the wood chunk and then deposited an egg. Female often did not bother covering such holes, sometimes just pushing  a little amount of softwood around it. Some L1 larvae  were also found in the substrate (garden soil mixed with mulched wood). I am not sure whether the eggs were deposited in the substrate, or just fell out of the wood chunks. Unlike some of my other stags, prosopocoilus bison larvae did not get too excited:) when I transferred them into the individual containers filled with original wood and fermented oak sawdust and initially preferred to keep chewing the original wood rather than the treated oak flakes. Only a few of them switched to the fermented sawdust right away. Would be interesting to see what size males I will get on my fermented flakes and whether these flakes are any good for the prosopocoilus bison larvae