What's That Bug? does not endorse extermination

Big Beetle Classification
February 26, 2010
These bugs were seen in an area of Brasil that is almost uninhabited, except for a select few farms, and groupings of indigenous tribes in a large preservation area, close to the Xingu river.
These bugs appeared after torrential rains, and came out at night – usually getting stuck on their backs, if they weren’t mating. The males and females differ, as one has a large horn. I have found several beetles that seem to have their characteristics, though haven’t found the correct name. Can you help? 🙂
Amaris in Wonderland
Rio Culuene, Mato Grosso, Brasil

Rhinoceros Beetle

Dear Amaris,
It is very often the case with Rhinoceros Beetles, Scarab Beetles in the subfamily Dynastinae, that the male possesses spectacular horns while the female is hornless.  It appears though that you may have submitted images of two different species.  The hornless close-up individual with the ridged elytra or wing covers appears to be a different species from the horned individuals in the long shot which look like they have smooth elytra.  Perhaps one of our readers will be able to provide more information than a subfamily name Dynastinae and the general common name for individuals in the subfamily Dynastinae, Rhinoceros Beetles.

Rhinoceros Beetles

Daniel and Amaris:
I can’t be certain because the images provide little sense of scale and the photo of the males is short on detail, but I will take a stab at it anyway. I think they are probably Rhinoceros Beetles in the genus Megasoma, possibly M. actaeon, which range across northern South America. These are very large beetles indeed (up to 12 or 13 cm long for males), so Amaris can probably let me know right away if I am off track. M. actaeon are sexually dimorphic, females are hornless and their elytra are rough (sort of like walnut shells), whereas the males are smooth and shiny. You can also check out the ‘Butterflies and Beetles of Argentina’ site (scroll down to the fifth image), or ‘Naturalworlds’ (two pages of photos and information). Regards.

What's That Bug? does not endorse extermination

One Response to Unknown Rhinoceros Beetles from Brazil: Megasoma actaeon maybe

  1. Dave says:

    While I don’t know what species these are, Dynastinae are eaten all over the world [I’ll post some images of Thai specimens I’ve got] in three out of four life-stages: larval/pupal/adult. The latter require some “peeling” of elytra and other parts, leaving what most call a ‘nugget’ of meat in the abdomen.


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