Spiders - Cobweb Weavers

This group represents the earliest of the web-weaving spiders. The silk spinning adaptation came out of the need to catch airborne insects. These spiders build horizontal lacey sheets of web, often close to the ground or on large surfaces like tree trunks, in which the spiders work from a tube-like retreat, racing out to trap insects falling on the sheet or, in the case of Comb-footed spiders like the Redback, trapped by the sticky lines to the ground.The webs of some Weavers are large, seemingly messy, three-dimensional structures - some appear to have multiple horizontal layers. Other spiders produce two-dimensional wheel-like webs (Orb Weavers, see below) with radiating support spokes connected up with a spiral of silk. This entire production may take as little as 20 minutes even though it involves over 1500 junction points and requires 10-30 metres of silk. The position and direction of the web is strategically placed in the flight paths of insects and often some distance above the ground, using tree branches as anchors. The design of the web allows the slightest vibrations to be transmitted along the web to the spider which usually sits in the centre of the wheel-like web.

 
The Weavers

One of the two main uses of silk was reproductive. All spider eggs are wrapped in silk and the male uses it when transferring sperm to his palps for mating. The use of silk for web-weaving came out of the need to catch insects which had evolved wings for flight during the Carboniferous and Permian periods. These large vertical webs capitalised upon the new abundance of flying insects.

This web style maximises the spider's insect catch while requiring the least amount of energy to produce. The position and direction of the web is strategically placed in the flight paths of insects and often some distance above the ground, using tree branches as anchors. The design of the web allows the slightest vibrations to be transmitted along the web to the spider which usually sits in the centre of the wheel-like web. Some of the spiders in this group are the largest in Australia. The Golden Orb Spider maintains the web as a long term structure while the Garden Orb disassembles, consumes and quickly recycles the silk from its strong web each night.

 
Golden Orb Spider (Nephila pilipes)

This spider's common name comes from the colour of its large web but it could have just as easily been called the Bird-trapping Spider! With a permanent, strong web measuring one metre (just over 3 feet) in diameter which is strategically placed in flyways between trees, it is no wonder that small birds and insectivorous bats sometimes get tangled up in it. The females of the Golden Orb reach an imposing 45mm (nearly two inch) body length but they are basically harmless. Like many of the larger web-building species, these spiders tolerate other small species of spiders to cohabit their web in a kleptoparasitic relationship (in some cases, the smaller spider feeds at the mouth of its giant host). Commonly encountered in the Wet Tropics and south to Brisbane, the Golden Orb can also be seen around buildings. The yellow colour of the web attracts insects.

 
Black House Spider (Badumna longinqua)

You are more likely to see this spider around your home or resort than you would out in the forest. This medium sized, stocky black spider has a messy web with one or more entrance funnels through which the spider can be seen during the day. Moths are the favourite food of the House Spider which has the good sense to position its web strategically in the corners of windows or under eaves or awnings. If you desire to rid your windows of this spider's untidy web, please do so carefully with a broom so as not to invoke a bite. Although it is not sufficiently toxic to cause permanent harm, you will remember the pain for quite some time and you may experience other unpleasant side effects.

 
Garden Orb Spider (Eriophora transmarina)

Another spider of impressive bulk is the furry-looking Garden Orb Spider. A tell-tale indication of this species is that the upper portion of its legs are devoid of hair, having instead exposed maroon shiny skin.

Every night at dusk, this spider emerges from its daytime resting place on a nearby tree or shrub and creates its meticulous web in about an hour's time. By morning, the success of its feeding is evidenced by the breaks in the connecting threads. As the sun rises, the Garden Orb eats all of its web except for the anchor lines. These will remain in place throughout the day to provide the foundation for the next night's weaving. These lines are not sticky but are so strong that a person bumping gently into one will not break it unless a little force is applied.

The Garden Orb hangs its large web vertically in the flight paths of insects. As soon as the prey has touched the sticky web, the spider rushes out to bundle it in silk, spinning the meal round and round as it dispenses copious amounts of silk. From there, the victim is carried to the centre of the web and eaten straight away or hung nearby for later. Despite its fearsome appearance, the Garden Orb is relatively harmless and might even vacate the web if it is sufficiently threatened. Its bite is not thought to be particularly dangerous, but can be painful.

 
Spiny Spider (Gasteracantha fornicata)

This strange little spider has the distinction of being the first spider in Australia collected by Captain Cook's crew. It is an unmistakable spider with a colourful hard outer shell painted in vibrant yellow, horizontal stripes against a deep maroon background. The small (6-10mm/¼-½ inch) body and very short legs are also maroon. A total of six spines protrude from the sides and bottom end of the 'shell' and this seems to dissuade birds from making a meal out of them.The common name derives from the latin name for arch (its abdomen is arched).

Commonly seen in the forest or in your backyard, the Spiny Spider is not toxic but has a sharp bite. Its web is usually not far from the ground, often being attached to shrubs or fences so it is an easy spider to find.