I was glad to visit the Singapore Botanic Gardens a week back on 5th of June to attend a talk by Dr Linda S. Rayor, who had come all the way from the Department of Entomology, Cornell University in the US. She is a highly regarded spider expert – having been featured in the documentary series Monster Bug Wars. Dr Rayor explained that spiders are not insects, as they belong to a different class of invertebrate animals called Arachnids. Most spiders have eight legs and eight eyes, unlike insects which usually have six of each.
Dr Rayor herself answered the question that may have been on a few people’s minds, “How did a nice girl like her get interested in spiders?” Having grown up in Colorado, a relatively spider/small animal species free place – her move to Kansas for undergraduate studies opened her eyes to a lot of wildlife including spiders. She initially studied molecular biology and found it was not really up her alley and took several modules on animal behavior and later switched to the study of spiders.
Dr Rayor shared some interesting information about spiders, and I write here a few nuggets from her talk, while using pictures of her slides with her kind permission.
1.How numerous are spiders on earth? Spiders are the dominant terrestrial predators on earth, and are important for maintaining ecological balance due to the abundance of insects they prey on. Dr Rayor shared this slide to show that the number of species of spiders more than the number of mammals (as depicted by the size of the spider relative to that of the elephant) in this picture below relative to other species.
There are 5,490 mammal species in all. There are 5,950 jumping spider species alone. Over 46,733 spider species have been identified from an estimated 170,000 spider species on earth.
2. How pervasive are ‘jumping’ spiders? Jumping spiders are the largest family of spiders, have good vision and are capable of agile jumping. There are at least 100 jumping spiders in Singapore, several of whom have been diligently captured through the lens by Nicky Bay whose brilliant photography of spiders and insects are captured in his flickr ablum . If you are interested in learning more about the spiders of Singapore, Dr Rayor pointed to this guide by Joseph Koh, David J Court and Chris S P Ang called, “The Taxonomic Guide to the Spiders of Singapore”
Jumping spiders are found all over the world (including on top of Mt. Everest) with the exception of Antarctica. Darwin had reported finding spiders on the sails of HMS Beagle, 500 miles off Galapagos island. Light weight spiders use a technique called ballooning – where they spin silk from their back. As hot air rises, the silk wafts up with the hot air like the tail of a kite, and spiders can get high into the upper atmosphere and can travel hundreds of kilometres. Spiders are one of the first creatures to balloon into disrupted habitats such as volcanoes.
3.Why do spiders have hair? Spiders eat food a bit differently from others in the animal kingdom. They have a narrow oesophagus, so when they catch prey, they inject venom which helps the food dissolve outside the body, which they suck up like a protein milk shake. All spiders have hair in front which acts as filters to keep out the solid part of the food. Spiders also have fine hair on their bodies that helps them sense their environment.
4.What do spiders eat? All spiders are predators, and eat a variety of insects and vertebrates including lizards and frogs, with some bigger spiders having been spotted eating bats and small birds though this is quite rare. Spiders can eat other spiders so some are cannibalistic. In some species of spiders, the larger female eats the smaller male spider before or after mating.There’s only one species of ‘vegetarian’ jumping spider – Bagheera kiplingi from Mexico, which eats the fruit of the acacia plant. This constitutes 80% of its diet, the rest of its diet is like that of other spiders.
5. Why do spiders make webs? Spider webs are a way for it to extend its sensory perception, as it can sense whatever comes on its web. Webs are very useful to catch prey.
Dr Rayor also spoke of the orge faced or net casting spider has a unique way of spinning its web. It builds an orb web on its front legs like a net, with which it captures prey.
6. How do baby spiders survive? Spiders come out of the egg sac, and once they moult, pretty much look like smaller versions of adult spiders and essentially survive on their own, unlike other species like butterflies which goes through metamorphosis.
7.Are spiders intelligent? It was fascinating to hear from Dr Rayor that some spider species such as the Portia sp have the capacity for learning and problem solving, traits that are usually attributed to larger animals– and that there is some research in studying their different ‘personalities’. Portia is a genus of jumping spider that preys on other spiders. They learn by trial and error when hunting for unfamiliar prey or in unfamiliar situations, and then remember what they have learnt.
8.How venomous are spiders? All spiders secrete venom, but 6 groups of spiders have venom that are toxic to humans. The Brazilian wandering spider (found in Brazil and some Latin American countries) is the most venomous, followed by the Sydney funnel- web spider native to Australia and the Black Widow (found worldwide). There are no known venomous spiders in Singapore.
Dr Rayor quoted research about non-addictive pain killers being derived by Australian researchers from spider venom, as they found that 40% of spider venom had peptides that block pain.
Dr Linda S. Rayor’s research at Cornell University is now focused on social spiders – or spiders that live in communities. She has been studying the evolution of sociality in Australian huntsman spiders. Only about 1.5% of spiders are social, and live in communities or colonies. We don’t have any species of social spiders in Singapore.
After Dr Rayor’s interesting talk, I’m certainly going to pay closer attention to the tiny jumping spiders that pop up on my study table occasionally, and when I go out exploring in nature reserves. I hope you become more interested in spiders too! Maybe you’ve seen some really interesting or intriguing ones, please tell me about your encounters in the comments! I would love to hear about them.
Other links you may be interested in:
- Dr Rayor’s career history : CV Dr Linda S. Rayor
- Dr Rayor’s YouTube channel: YouTube.com/NaturalistOutreach
- Monster Bug Wars where Dr Rayor has been featured
- Some blogposts where I’ve mentioned spiders: Taman Negara , Golden Spider