Just so story #3 ; Why the king of the undergrowth has to be so strong…

One of my ‘Species Saturday’ posts for OuTrop …
Although I survey primates and help catalogue the distribution/numbers of the main felid species seen in the Bornean site I work on, I also do a lot of biodiversity work. Understanding the flora and non-mammal species of an ecosystem is vital to plan how best to conserve an area. Here I focus on possibly the king of the undergrowth…
“The big and the beautiful in the insect world; the stunning rhinoceros beetle!


Of course their ‘rhinoceros’ common name refers to the characteristic horns, which only the males have. Each male has a pair of horns. These horns are used to fight other males during mating season, and for digging. as ever with such large morphological investments, if an individual has a large horn, it is a good indicator that the individual is in good physical health. The winner of the fight generally has the larger horn and it is the winner that gets to mate with the female.
This ensures the genes for the stronger individual are passed on, making evolutionary sense for the population in general!

Female in a butterfly trap ©OuTrop

These amazing creatures are black, shiny and a true beauty of the insects! Known to support items up to 100 times their own weight! The alternative name of Hercules beetle is hardly a surprise… With their thick exoskeleton, they are particularly strong… which can be quite a shock when they try and crawl away from your grasp with some force! Indeed their best protection from predators is their size and stature. When OuTrop conducted our butterfly surveys, we often found them in amongst the banana-smush bait – a nice chance to see them up close, as mostly they are nocturnal. Rhinoceros beetles do fly but generally for short distances – shifting that weight takes some doing!
Rhinoceros beetles (subfamily Scarabaeidae – the scarab beetle family), includes over 300 species. Their unique shapes and large size makes them fantastic insects to stubble upon in the forest; among the largest of the beetles (sometimes reaching more than 6 inches in length) but harmless to humans and fascinating to see close up. Here in Borneo we find individuals from the Chalcosoma genus – the Southeast Asian rhinoceros beetles.
Some species, when disturbed, release very loud, hissing squeaks. These noises are created by rubbing their abdomens against the ends of their wing covers – the species we see don’t make this noise – so the cicadas still get the prize of noisiest Sabangau insect!

An iridescent individual

Amazingly, these beetles’ larval stages can last for several years. The larvae feed on rotten wood and the adults feed on nectar and fruit – explaining why we find them in our butterfly traps! Don’t let appearances fool you – adult rhinoceros beetles don’t eat too much, but their larvae eat a lot of rotting wood allowing them to pupate into their large, impressive, black selves.

For more information on Coleoptera and recent action within the UK Biodiversity Action Plan helping to describe the biological resources (including beetles!) of the UK in order to help conserve and aid recovery of species under threat or endangered, see here from the Natural History Museum.
©Thea Powell”


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