Jumping Spiders
Tasmania has an amazing diversity of spiders. They include funnel-web spiders, huntsmen, cave spiders, orb-weaving spiders, wolf spiders, but my favourite are the family of jumping spiders.
Around the world, jumping spiders make up the largest numbers of genera of any family of spiders with 645 described genera and thousands of species. Here in Tasmania I have recorded more than 75 species of the tiny creatures and am finding more each year. Many of these have not been described.
Adult jumping spiders can vary in length from about 3 mm up to 13 mm. They are diverse in shape and colour and have a character that makes them both adorable and amusing to observe. Some of the species exhibit sexual dimorphism where the males and females look quite different. This often makes it difficult to identify the species unless the pair are found together in close proximity.
These tiny spiders are hunters who don’t build a web to snare their prey, but will stalk an insect and when within jumping range will pounce and immobilise the insect, which can often be much larger than they are. They use a thread of silk as a safety line when they jump in case they miss their target and can then climb back to their starting point of the jump.
Jumping spiders have two unusual features which make them unique from other spiders. They have the ability to independently move their cephalothorax – the front part of the body which is both head and thorax – from the abdomen. This gives them the ability to look around them when hunting. The second feature is the eight eyes. The central two are large and can observe the prey from a distance and the rear two are located well back on the cephalothorax so they can see behind them. With the array of eyes, they have an almost 360º range of vision.
When photographing jumping spiders, I always take diagnostic images as an aid to identification. These consist of a dorsal image, frontal view as well as a ventral image. However, as jumping spiders have such interesting personalities, I allow them to walk on my hand while I follow their antics with the camera in order to get more artistic images. This often leads to the spiders jumping onto the lens of the camera as they see themselves reflected in the lens.
In order to positively identify a spider, arachnologists rarely depend on the look of a live spider. They often never see a living spider, but work with spiders which have been collected and preserved in Ethanol. With these, they study the features, which make a spider species unique. These include the male palps and female epigyne which are the sexual organs of spiders, plus features such as spines on the legs, spinnerets, preening combs and eye layout.
While jumping spiders have fangs and are venomous to their prey, they are essentially harmless to humans and can be handled comfortably, making them easy and a lot of fun to observe their behaviour. So you see, not all spiders are creepy.
John is a retired teacher who became interested in photographing spiders, which led to trying to identify them. He began a website to document the spiders he found and photographed (www.tasmanianspiders.info)and produced a book of Tasmanian spiders. He is an Honorary Research Associate at the Queen Victoria Museum in Launceston.
