I had not seen such a large, colourful beetle before, and definitely not one with such an ornate y-shaped horn projecting from its face. This beetle is so large and distinctive, at least it should be easy to identify I thought.
I was wrong! After lots of searching I have not been able to find an identical-looking beetle in all the places I have looked. I am pretty certain it is in the Scarabaedae family of beetles – known as scarabs – which is a huge family comprising 30 000 species worldwide and about 3000 species in southern Africa. So if the large beetle in our garden is a scarab, to find exactly which species it is out of so many might be a bit needle-in-the-haystackish.
When I first spotted the beetle on an overcast morning after light rain, it appeared to be fast asleep among the leaves of a Lebombo cluster-leaf sapling
I read that the family of scarab beetles includes dung beetles, chafers, rhinocerous beetles, and Goliath beetles among its members. After finding photos of some similarish beetles, I wonder if perhaps this beetle is a fruit or flower chafer, perhaps in the tribus Goliathini, maybe in the genus Mecynorhina? Any suggestions would be very welcome.
And here it is still sleeping, photographed from the other side
When I say this beetle is large, it is actually about 6 cm (2 inches) in length. Of course larger beetles do occur, but this is the largest beetle I have seen in our area. Such a horn usually occurs only in males, and it is used for fighting over mates or resources.
Here is a rear view of the beetle. I fancy that the two black dots, resembling eyes might perhaps be a deterrent to predators
One of the distinctive characteristics of scarab beetles is the antennae. At the tip of each antenna a club-like apex comprises 3-7 flat, moveable plates, which can be fanned out to scent odours.
In this photo of the beetle, the antennae with the ends furled into clubs can be seen on either side of the two-pronged horn
All beetles undergo four phases of metamorphoses – from egg to grub-like larvae, to pupa, to adult beetle. The larvae resemble pale slightly curled caterpillars and they mostly live underground or under plant debris and are not exposed to the sun. Adults and larvae of scarab beetles, depending on the species, eat fresh or decaying plant matter, nectar, dung and fungi. Fresh plant matter may include fruit, flowers and sap.
All six legs of this beetle end in a forked “foot” that appears to be adapted for hooking onto things rather than grasping. Although this beetle seemed to be rather clumsy, it did manage to hook onto a leaf when hanging upside down underneath
Here is the beetle partially concealed as it hangs upside down under a leaf, using its hooked ‘feet’ or ‘toes’ to hang onto the leaf
A close-up the beetle keeping a low profile and showing its jointed legs and hooked ‘toes’
I kept an eye on the beetle off and on throughout the morning. It moved from its sleeping spot to spend quite some time under a leaf and then as the temperature rose slightly as the cloud cover thinned it moved out onto the top of a leaf as if to warm up. With hindsight I think that perhaps it was warming up in preparation for flying.
The beetle apparently warming up in the glow of the sun that is penetrating through a thin layer of clouds and radiating a degree of warmth
Just after I took the above photo, the beetle started moving around and fell off the leaf. I bent down to see it hanging under another leaf that was lower down, but it fell off that leaf too, as can be seen in the video below. The second time it fell to the ground, it crawled to the stem of the small tree and started climbing back up and then, before I could get my camera on it, it suddenly launched itself off the stem and took flight, bumbling off rapidly to disappear through the trees and not to be seen again.
In this short video, not a lot happens, but it does show something of the beetle’s rather other-worldly quality. Oh and by the way, the tinnitus-like background noise is actually the sound of chorusing cicadas.
So, discovering this beetle has been rather tantalising, and it seems remarkable that I have not been able to identify such a large and distinctive beetle – but then the 3000 species of scarab beetles in southern Africa won’t all be covered in illustrated reference books, field guides and websites. And in a way, the lack of identification adds to its rather extra-terrestrial demeanour and allure.
References: Picker, Mike, Griffiths, Charles & Weaving, Alan. 2019. Field Guide to Insects of South Africa. Cape Town: Struik Nature; Wikipedia. 2019. Scarabaeidae. https://en.wikipedia.org/wiki/Scarabaeidae
Posted by Carol