Spiders
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Biology
Apart from several types of indigenous Australian spiders, whose bites are often dangerous and occasionally life threatening, most are relatively harmless. However, they sometimes bite humans that encroach on their habitat. Any spider bite should receive medical attention as blood poisoning or an infection could possibly result.
Apart from widespread and sometimes pathological fear of spiders, the most common reason for control is the elimination of unsightly webs.
Spiders can be readily distinguished from insects: they have 8 legs instead of 6 and they have 2 body segments instead of three – the head and thorax are fused into one unit which contains eyes, mouthparts and legs. The abdomen section is soft and also houses the reproductive organs, the silk glands and spinnerets, and the respiratory openings that are visible on the under surface like the pages of a book. This large surface area achieves the transference of oxygen into blood. There are usually 4 pairs of eyes; each a simple lens. The arrangement of these eyes in a pattern is constant for each species and is an aid to identification. The fine hairs and setae on various parts of the body are said to be sensitive to taste, touch and vibration.
Habits
Most spiders, being nocturnal, are seldom seen during the day unless disturbed. Those which depend on webbing to snare their prey seldom move far and hide in a crevice, curled leaf or appear camouflaged as twigs. Hunting spiders such as the huntsman are ground dwellers and are not dependent on webs for food.
Males seek out females at mating time. Male spiders have long palps alongside their jaws. These sometimes could be confused as another set of legs, but they are long for the purpose of picking up their sperm and depositing it in the genitalia of the female. After mating, the male often becomes an immediate high protein meal to assist the egg production of the female. The eggs are usually deposited into a silken sac produced by the female. The spiderlings hatch inside the sac and moult once before they emerge. They must find their own food and disperse quickly in search of it. By successive moults they become adults and those that survive can usually be expected to live for up to 3 years.
Whether the spider traps prey in a web or hunts to capture it, the victim is injected with venom through the fangs. This immobilises the prey. The body is then squeezed and the erupting liquid is sucked in through the small mouth behind the fangs at the base of the palps. Most species can survive for months without food. This is just as well, as insect prey is usually scarce in the cold winter months.
Silk or web is produced from glands in the abdomen and deposited through the spinnerets. The orb weaving spiders produce an adhesive silk for the snare area of the web and their drier silk for the radii and guy lines. In some species, spiderlings let out sufficient web into the air to lift and carry them away.
Management
As with all pest management programs, an Integrated Pest Management (IPM) approach is an integral part of successful spider control. All control procedures are preceded by a thorough inspection of the entire premises to define the extent of the problem. Precise application is favoured over ‘blanket’ spraying and sometimes even changing the position of the colour of nearby lights can reduce the number of insects attracted to them and hence the spider population.
Hunting spiders such as the huntsman and white tail spider are difficult to control with residual chemicals as there is no web to treat. In these cases it is usually best to target the spider’s food sources instead, such as red back spiders.
For more information or to make a booking contact Envirotechnics on (08) 6461 5700.
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