Recyclers of the rainforest: Bornean myriapods, millipedes (Diplopoda), and their nemesis, giant centipedes (Chilipoda)
Rainforest romance ensues when randy red millipedes (Trachelomegalus modestior) of Borneo get face-to-face.
Clusters of strange “noodle” millipedes (Pseudodesmus sp.) frequent decaying logs in the Bornean rainforest.
With terrestrial insect life in the wild mostly battened down for winter in much of North America, it’s time to get out of town to warmer places. We head to the tropics to meet some of the most fascinating arthropods on the planet. First stop, Borneo, the third largest island on earth where we visit Gunung Mulu National Park and Tabin Wildlife Reserve. At some 130 million years of age, the Bornean rainforest is one of the oldest and most diverse places on the planet. Populated by some 10,000 species of plants that provide food and homes for an estimated 3,000 species of arthropods, Mulu and Tabin are ideal locations to discover insects and their allies.
Guess why these rainforest recyclers in the genus Stenoniodes are called tractor millipedes.
Year-round warmth and stupendous rainfall make tropical rainforests one of the most productive ecosystems on earth and this phenomenal bounty of plant material provides untold opportunities for many of Mother Nature’s most important recyclers. Premier amongst the arthropod recyclers are millipedes, a coterie some 400 million years old. These detritivores shred and consume organic matter including mosses, algae, fallen trees, and decaying vegetation that carpet the forest floor.
Millipedes belong to the subphylum of the arthropods called Myriapoda, those with “many feet.” Do they really have a thousand feet? Nah, they don’t really have feet, but they do have legs and the record number of legs for a millipede is somewhere north of 700. However, most millipedes have fewer than 400 legs. As millipedes molt and grow, body segments with two pairs of legs are added.
When under attack by a predator, giant pill millipedes (Sphaerotheriida) go armadillo and curl into a defensive ball to foil attacks by would-be predators.
Millipedes live many years and can produce hundreds of offspring during their lifetime. Millipedes do not bite or sting, but several species such as those we met in a previous episode secrete noxious chemicals from glands lining the margins of their body. Noxious chemicals are not the sole defense of these rainforest recyclers. Some like the giant pill millipedes can curl into a ball, tucking their head and vulnerable underbelly beneath a sphere of hard armored plates impenetrable to many rainforest predators.
But danger prowls the rainforest floor in another member of the myriapod clan, Pacific giant centipedes. These fierce predators bear but one pair of legs on each body segment. Two highly modified legs just beneath the head called toxicognaths are poison claws which deliver a highly toxic, lethal bite to hapless prey, including many arthropods and some small vertebrates. In addition to millipedes, spiders, scorpions, mice and lizards may be on menu.
Highly modified legs called toxicognaths deliver lethal venom to victims of predacious centipedes.
Centipedes locate prey by sensing vibrations in the surrounding substrate. Once detected, a vicious assault ensues. First, a potential meal is snared by legs near the head of the centipede and then embraced with several sets of legs while the toxicognaths inject venom into the prey. While the venom takes effect, the perfidious embrace prevents the prey’s escape. Once subdued, the prey is chopped into small pieces by two pairs of jaws and the tasty meal enters the centipede’s maw. Pacific giant centipedes now occupy several continents and dozens of islands around the world.
Should you have the good fortune to encounter one of these carnivorous creatures, use caution. The poison-claw-pinch of the centipede is extremely painful and is potentially lethal, so if you encounter one, please avoid the urge to cuddle it. Next week, we return to the rainforest to meet more six-legged wonders.
A walk in the Bornean rainforest reveals strange serenades and a rich assortment of millipedes, key recyclers of organic matter. Along a shady boardwalk a pair of red millipedes (Trachelomegalus) get romantic and glam for the camera. Nearby, “noodle” millipedes (Pseudodesmus) cluster on a decaying log. Romance is also afoot on the forest floor where tractor millipedes (Stenoniodes) get it on. When harassed by a predator or bug geek, giant pill millipedes (Sphaerotheriida) go armadillo and curl into a defensive ball. But danger awaits these recyclers and other small animals in the form of giant predacious centipedes (Scolopendra). The underslung venomous claw of centipedes delivers a lethal puncture to prey or fiercely painful and potentially life-threatening wound to humans.
Acknowledgements
Several offerings by iNaturalist and Wikipedia were used to prepare this episode as were “An Introduction to Insects” by D. J. Borer, D. M. DeLong, and C. A. Triplehorn, and “Secret Weapons” by T. Eisner, M. Eisner, and M. Siegler. We thank our intrepid guides, Larry at Mulu National Park and Oliver at Tabin Wildlife Reserve for braving the rainforest after dark and Dan, Kristie, Bob, Pat, and Paula for spotting, wrangling, and documenting creatures featured in this episode.
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