March 3rd is World Wildlife Day! ISTS is kickstarting a new series – ‘Weird, Wild, Wonderful’, where we will be sharing about Singapore’s less well-known flora and fauna. This week, we’re exploring our local arachnids.
When you hear the word ‘arachnid’, you’ll likely think of spiders, but there are stranger cousins to the spiders. Arachnids refer to a group of organisms with 6 pairs of appendages. In addition to their 4 pairs of legs (8 legs), arachnids also have 2 pairs of mouthpart appendages. The first pair are called chelicerae (commonly referred to as the “jaws”), and the second are called pedipalps, which can look quite varied across arachnid types. Some arachnid pedipalps look very much like their legs (e.g. spiders). Others are pincered (e.g. scorpions). The third kind of arachnid pedipalps are raptorial, used to grip prey between pedipalp segments (e.g. whip spiders).
Although the lesser-known arachnids are unfamiliar to most, they can be surprisingly easy to find. A walk along any of our publicly accessible trails in our nature reserves, nature parks, parks and gardens, and even park connectors can reveal these hidden wonders. Seven lesser-known arachnid groups are featured in this article.
Scorpions (Scorpiones)
The most commonly known arachnids following spiders are the scorpions. Scorpions are best recognized from their two pincers and stinging tail. They are fearsome predators, often preying on other predators like spiders and centipedes.
This 1.5 cm long scorpion was seen crawling on a railing post in Singapore Botanic Garden’s Rainforest Walk. Notice its big pincers and relatively tiny stinging tail! It is fairly common to see these scorpions on trees trunks, hiding among cracks in the bark. 
This mother scorpion (Lychas scutilus) carrying her young was spotted on a low-growing plant less than 3 feet from a boardwalk railing in one of our nature reserves. These scorpions are fairly common and may also be found wandering about on tree trunks or hiding in holes on trees.
Pseudoscorpions (Pseudoscorpiones)
Pseudoscorpions are tiny creatures (<5mm long) with two pincered pedipalps, just like scorpions but without the stinging tail. They also have venom, but unlike scorpions which use their tails to sting, pseudoscorpions use their pincers to envenomate prey.
Psuedoscorpions are also often found living in tree bark. Here, a colony of pseudoscorpions living on a tree trunk have captured a praying mantis. 
A different species of pseudoscorpion, with much slimmer claws, was spotted on a broad leaf of a plant along a park connector. Similar- looking pseudoscorpions may also be found amongst leaf litter. 
Pseudoscorpions are usually found hiding in the cracks of boardwalks. This one was spotted on a plank (boardwalk’s metal bolt for scale).
Harvestman (Opiliones)
Harvestmen are very similar to spiders in having eight legs, but the connection between their heads and bodies are so broad they look like they only have one body section.
A harvestman (Epedanidae) with fearsome looking pedipalps. It was found walking among leaf litter in a local nature park. 
A harvestman with a mushroom cap in its chelicerae and pedipalps. 
This individual (Sandokanidae) found wandering onto a dirt path in a nature park is another relatively commonly seen harvestman. It smelled faintly of antiseptic solution, likely from chemicals it releases as a defense mechanism.
Mites (Acari)
Mites are probably the most abundant group of arachnids. They are tiny arachnids found practically everywhere. Ticks and dust mites are probably the most commonly encountered mites, though there are also stranger-looking mites out there.
This red mite (Trombidiformes) was found riding on the eye of a moth. Parasitic red mites are often seen on insects and spiders, feeding on the bodily fluids of their hosts. These mites are typically juveniles; when they mature, they become free- living predatory mites. 
Also spotted at a park connector was a mother daddy-long- legs spider carrying her egg sac along with a host of parasitic red mites. 
A mature Trombid mite spotted on a leaf along a park connector. 
Tiny black mites (Oribatida) such as this one are very commonly seen on tree bark in any of Singapore’s nature spaces. They look like tiny black balls to the naked eye.
Whip scorpions (Thelyphonida)
Whip scorpions are not so commonly seen, and usually found in our nature reserves. They spray a foul-smelling defensive chemical when disturbed, hence it’s common name “vinegaroon”. Their pedipalps are strongly built, pincered, and used to hold prey. Their first pair of legs are long and thin, which they use to sense their surroundings.
Whip spiders (Amblypygi)
Whip spiders are some of the most-scary-looking arachnids. However, they are fairly harmless to humans. Their pedipalps are spined and used to grip prey. Their first pair of legs are very long, thin, and whip-like, which they use to sense their surroundings. A whip spider was featured as an unwitting victim of a curse in Harry Potter: The Goblet of Fire.
Short-tailed whip scorpions (Schizomida)
Schizomida are one of the least-known arachnids in Singapore. As they are usually tiny (about 5 mm long), they are not often seen. They are however likely to be quite common, being found even in house gardens. Like the whip scorpions, they use their first pair of long thin legs as sensory organs, and their strongly-built pedipalps to grip prey.
Singapore’s arachnids are not very well studied. Still, a good place to start might be at our Lee Kong Chian Natural History Museum, which has a local biodiversity website that can help with identification. There is also a book on Singapore Biodiversity that contains some information on our arachnids.
Arachnids camouflage and blend in well with their surroundings, but the symmetry of their bodies, as well as their movement, usually give them away. As you explore our nature reserves, pause to carefully examine tree trunks, fallen logs, cracks, and holes, which are the favourite hangout spots for arachnids. Take a closer look at that small piece of bark, stick, or bit of dirt; it might turn out to actually be an arachnid!
Leave a comment and tell us what you would like to see next in our Weird, Wild, Wonderful series!
Written by James Koh
Photos by James Koh
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