Spiders

Spiders belong to the arachnid group and have a body structure that distinguishes them from insects. They have eight jointed legs and their bodies are divided into two main sections: the cephalothorax and the abdomen.
 The cephalothorax is the combined head and thorax region and carries the spider's legs, eyes, mouthparts and pedipalps. The pedipalps are a pair of appendages located at the front of the spider and are sometimes mistaken for an additional pair of legs. They have a sensory function and, in adult males, also play an important role in reproduction. The abdomen forms the second main section of the spider's body and contains many of its internal organs as well as the spinnerets used to produce silk. Depending on the species, the spider's body and legs may be heavily or sparsely covered with hairs. Although Australian spiders vary considerably in size, colour and appearance, this basic body structure is shared across true spiders.

Spider identification involves looking at a combination of physical characteristics rather than relying on colour or size alone. Many Australian spiders can appear similar at first glance, and appearance may also vary between males, females and different stages of development. Features used to help identify spiders include body structure, leg shape and length, markings, hair coverage and the arrangement of the eyes. Most spiders have three or four pairs of eyes positioned on the cephalothorax, and their arrangement can provide an additional identification feature. Adult males and females of the same species may also look quite different. Male spiders are commonly smaller with proportionally longer legs, while females generally have a larger abdomen. The pedipalps at the front of the spider are typically more prominent in adult males and can also assist with identification. Where accurate identification is important, particularly when a spider may be of medical significance, identification should not be based solely on its colour, size or general appearance.

After mating, the female spider produces an egg sac made from silk, which contains numerous eggs. The size, shape and location of the egg sac vary between spider species. Some spiders leave their egg sacs within or close to their shelter, while others attach or protect them in suitable locations. The eggs hatch inside the egg sac and the young spiders, known as spiderlings, moult before emerging. Once they leave the egg sac, most spiderlings must find their own food and begin developing independently. Some spiderlings disperse by a process known as ballooning. They release fine strands of silk into the air which can be caught by the breeze, allowing the small spiders to become airborne and move away from their original location. This helps disperse young spiders and reduces competition in one area. As spiders grow, they pass through a series of moults before reaching adulthood. Immediately after moulting, the spider's new outer covering is softer and paler, gradually hardening and becoming darker. Development time varies considerably between different types of spiders. Many web-building spiders complete their life cycle in less than a year, while some ground-dwelling spiders develop much more slowly and may live for many years.

Spiders occupy a wide range of habitats, and their behaviour varies considerably between species. Many spiders are most active at night, spending the day sheltered before emerging after dark to search for prey or construct and maintain their webs. Web-building spiders select locations where their webs are protected and where insects are likely to be available. Around homes and businesses, these spiders may establish themselves in areas such as eaves, window frames, corners and other sheltered parts of buildings. In natural environments, spiders may be found among vegetation, beneath loose bark, in leaf litter and other protected locations. Ground-dwelling spiders have different habits. Some live in holes or burrows in the soil, while others shelter and hunt at ground level or within leaf litter. Certain ground-dwelling species may leave their usual habitat and wander, particularly males searching for a mate or spiders disturbed by environmental conditions. Spiders are predators and feed primarily on insects and other arthropods. Web-building species use their webs to capture prey, while other spiders actively hunt or wait for prey to come within reach. The availability of insects, suitable shelter and protected harbourage can therefore influence where spiders become established around a property.

Spiders become a problem around homes and businesses when they establish themselves in areas where people live, work or regularly pass. Web-building spiders can produce extensive webbing around eaves, windows, verandahs, garages, sheds and other sheltered areas, affecting the appearance of a property and becoming an ongoing nuisance. Properties that provide suitable shelter and a regular supply of insects can support continued spider activity. Protected areas around buildings provide places for spiders to establish webs and harbourage, while insects attracted to the property provide a readily available food source. Some spiders may also enter buildings while searching for shelter, food or a mate. Ground-dwelling spiders can sometimes wander into yards, garages, sheds and homes, particularly when disturbed by wet weather, landscaping, excavation or changes to their usual habitat. Spider activity can also create concern because Australia is home to species capable of medically significant bites. Correct identification and an understanding of where the spider is living are therefore important when deciding how the activity should be managed. Because web-building and ground-dwelling spiders behave differently, spider management should be based on the type of spider present and its habitat rather than treating all spider activity in the same way.

Professional spider management begins with identifying the type of spider activity present and the areas where spiders are living, webbing or harbouring. The treatment approach will vary depending on whether web-building spiders are established around the structure or ground-dwelling spiders are present. For web-building spiders, treatment can be targeted to suitable areas around the building where spiders and webbing are active. These may include eaves, window and door frames, external walls, garages, sheds, verandahs, fences and other protected areas. Existing webs can also help identify areas of established activity. Where appropriate, accessible roof voids, subfloor areas and other harbourage locations may also be inspected and treated when spider activity is identified. Ground-dwelling spiders require a different approach. Blanket spraying of lawns, gardens and surrounding ground is not considered an appropriate method of control. Effective treatment relies on locating spiders or their harbourage and applying treatment directly where appropriate. Because spider species, behaviour and habitats differ, a targeted treatment based on the activity found at the property provides a more appropriate approach than treating all spiders in the same way.

Environmental management can help make a property less suitable for spiders and reduce the conditions that encourage ongoing activity. Regularly remove old webbing from eaves, windows, verandahs, garages, sheds and other accessible areas. Reducing clutter, stored materials, rubble and leaf litter around buildings can also remove protected harbourage areas used by spiders and the insects they feed on. Vegetation can be trimmed where practical to reduce dense, sheltered areas immediately against buildings. Maintaining flyscreens and sealing suitable gaps around doors, windows and other openings can also help reduce spiders and insects entering the property. Outdoor lighting can attract flying insects, providing a food source for web-building spiders. Where practical, reducing unnecessary lighting or using lighting that attracts fewer insects may help reduce spider activity around buildings. When working outdoors, particularly around soil, vegetation, stored materials or rubbish, wear gloves and suitable footwear. Avoid leaving clothing, footwear, toys and similar items on the ground overnight, as wandering spiders may use them as temporary shelter. Extra care should be taken following prolonged wet weather, excavation, landscaping or other disturbances that may cause ground-dwelling spiders to leave their usual harbourage and wander into yards or buildings.