Overturned rhinoceros beetles – how do they get back on their feet? (study)

No matter how careful a beetle might be, there’s a fair chance that, sooner or later, it’ll find itself on its back. Raising the question, how does it right itself, i.e. get onto its feet again?

For current beetle-righting research turn to volume 28, Issue 2, 2016, of the journal Ecological Psychology where researchers professor Masato Sasaki and professor Tetsushi Nonaka [respectively of the Graduate School of Education, University of Tokyo and the Graduate School of Human Development and Environment, Kobe University, Japan] describe a set of experiments designed to provide some answers.

Beetles (more specifically Japanese rhinoceros beetles, Allomyrina dichotomus) were upturned on a variety of surfaces :
1. A trench in the floor,
2. A towel,
3. A fan,
4. A pan mat,
5. A sheet of newspaper,
6. A wooden toothpick,
7. A narrow ribbon,
8. A wide ribbon,
9. A plastic string,
10. A sheet of tissue paper,
11. A T-shirt,
12. A perilla leaf,
13. A sheet of scratch paper,
14. A disposable chopstick, and
15. The lid of a film case.

– to try and determine how they’d get the right way up again. Depending on the surface, the team noted various strategies and degrees of success (or otherwise). Here is the description for the Towel trial #2 (one of the more successful trials, as shown above).

“When the insect was turned upside down, a towel was slid on the floor to the left side of the beetle’s head. As the towel approached, the beetle oriented its head to it immediately and the two hind legs started to move in-phase, which resulted in the locomotion by pushing with the hind legs. The approach of a towel slipping over the wooden substrate surface may have shaded the part of optic array surrounding the beetle, or changed the air flow that could be sensed by its antennae, which seems to have induced the prospective extension of the leg on that side. Shortly after, the left foreleg came close to the towel and briefly touched it, and the left foreleg got entangled with the towel. Using this leg as a pivot point, the beetle pulled the whole body in such a way to roll. Subsequently, the tips of the right middle and hind legs also grasped the towel and the insect succeeded in righting itself. The leg of the insect was observed to release the cloth, which had been tangled tightly. However, how this was made possible is unclear. Duration: 3 s.”

See: The Reciprocity of Environment and Action in Self-Righting Beetles: The Textures of the Ground and an Object, and the Claws

The team came to various conclusions [for details see the full paper,  linked above] not least that :

“It is not improbable that various meanings of the habitat of an animal are embodied and embedded in the tips of the body-like claws.”

Note: After the experiments, the beetles were released back into the wild, where several promptly fell over again – but managed to quickly right themselves.

“This observation suggested that, in their natural habitat, it is not so difficult for beetles to right themselves after having been turned upside down.”

Also see: Geometry and self-righting of turtles and A Review of Self-Righting Techniques for Terrestrial Animals

 






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