Millipedes, or Shongololos as they are locally known are a common sight for Bushwise students during summer. Despite the disappointing sporadic rains thus far, these armoured tanks can be regularly seen trundling through the bush. Despite their numbers, they possess some fascinating adaptations and behaviour that make them a favourite amongst many guides to discuss with their guests.
It is worth noting that they are some of the most ancient species to have populated the Earth and fossil evidence shows that they have been around for over 450 million years! Back then, oxygen levels in the atmosphere allowed arthropods to grow to potentially terrifying sizes. Imagine walking through the bushveld and coming across a 2 meter specimen!!
The name millipede refers to their multiple legs (1000 feet) although it is worth noting that no modern day species have such numerous appendages. Each body segment has 2 pairs of legs (one of the characteristics that render them different from centipedes) and the longest recorded specimen was found in Kwa-Zulu Natal, boasting an impressive 182 segments and thus around 720 legs! Impressive yes, but still well short of the thousand legs suggested by its name.
In terms of ecology, millipedes are an integral part of the ecosystem and perform a similar role as that of the earthworm found in moister environments. Their habit of tunneling helps to recycle buried nutrients as well as allowing vital gases needed by plant life, such as nitrogen, to circulate through the soil. The majority of species are detritivores, feeding on decaying plant matter and thus form a vital link in the nutrient cycle to return this rich energy source back into the system.
Despite their rigid calcium and chitinous exoskeleton, they are vulnerable to predation but have developed a variety of fascinating defense adaptations to defend themselves. In addition to curling up into a coil to protect its more vulnerable legs (or a perfect sphere in the case of pill millipedes) millipedes can secrete a noxious compound through openings on their body. Anyone who has handled a millipede will be able to attest to the yellowish brown secretion that can stain fingers and even cause blistering in those with sensitive skin. This cocktail of chemicals can include kinones, iodine compounds and poisons such as prussic acid and even cyanide gas! Such is the potency of the latter that any small predatory insect that gets close to a highly agitated millipede may die within seconds! They are sometimes used in entomology as an effective killing agent in collection bottles. There is even one recorded human fatality whereby a young boy succumbed to the gas whilst sleeping in a room with hundreds of millipedes.
Other animals have found uses for this behaviour in terms of beefing up personal and home security. Wild dogs, various birds and even lemurs in Madagascar have been recorded intentionally harassing millipedes in order to stimulate this chemical production and then rolling in it. This is most likely to act as a repellent against biting insects and also a fungicide to deter ectoparasites. Hornbills too, regularly agitate millipedes and then paste them into the mud being used to seal their hole nests for the same reasons.
If the armour and chemical deterrents are unsuccessful, the millipedes have one last trick up their sleeve. If a quick escape is needed, they can flip on to their back and propel themselves away in a serpentine motion from danger at an impressive speed. Not only does this allow them to escape a predator, but the mimicry of a snake may well surprise its attacker, buying it vital seconds to reach safety.
Nature is resourceful however and even though the millipede has an impressive array of defensive strategies, various predators have evolved to beat the system. Mongooses roll and smash them against rocks to get rid of the worst secretions, whilst civets have seemingly developed a natural immunity to the millipede’s chemical arsenal. The most specialised predator however is conveniently named the ‘millipede assassin bug’ (Ectrichodia crux). The striking red nymphs hunt in packs whilst a full grown adult is more than capable of taking down a large millipede. Their proboscis is able to penetrate between the segments and injects a digestive enzyme that quickly paralyses its quarry, dissolving the internal organs so that they can be sucked out!
Knowledge and understanding of these animals are just some of the fascinating information that the current crop of Bushwise students will learn as they embark on their 6 month adventure to become fully qualified field guides!
Author: Ben Coley