Spiders – Common Species and how to prevent them?
My grandmother used to tell me that spiders were there to catch the flies, moths, cockroaches and mosquitos in the house. Integrated Pest Management (IPM) best practice concurs with her wisdom – spiders are amazing predators that can eat up to two times their weight in insects each day.
Despite their amazing ability to prey on insects, spiders can be annoying for those who clear their webs away and greatly feared by those who wouldn’t get near their web if you paid them. So whether you’re the one in the family everyone turns to when a spider turns up, or the one quivering until help arrives, here are some spider facts and safest options for how to manage them in your home…
“Unlike insects which use their mouths to groom themselves and ingest pesticides left in their path, spiders are not groomers. They have tarsi that enable them to move over surfaces that have been treated, and waxy cuticles protecting them from pesticide penetration. They are also able to close down their respiratory system to avoid inhaling pesticides”1
- The types of spiders that may be found in and around homes in Western Australia are most commonly daddy long legs, black house, wolf, huntsman, trapdoor, white tail and redback spiders.
- Spiders are nocturnal and hunt or create webs to catch their prey at night
- Spiders eat insects and are mostly found in the home where insects fall around light sources, and in cracks and crevices of walls and windows
- Unlike insects (which are mostly social creatures), spiders are loners and work on their own to catch their prey either by hunting or trapping in webs
- Although spiders are perhaps one the most feared organisms, the only lethally venomous species in Western Australia, is the redback (Lactrodectus hasselti). Anti-venom was developed for redbacks in 1956 with no deaths since 19551
- Despite reports that white-tail spider bites can cause necrotic ulcers, recent research has found this very unlikely, however, their bites can cause a painful red lesion with minor effects in most cases2
- Unfortunately one of the greatest misuses of pesticides is broad spectrum residual applications for spiders. These applications are largely ineffective because spiders are only poisoned when they are directly sprayed with the pesticide, and such treatments are more likely to disturb spiders and provoke spider into biting3. Unlike insects which use their mouths to groom themselves and ingest pesticides left in their path, spiders are not groomers. They have tarsi that enable them to move over surfaces that have been treated, and waxy cuticles protecting them from pesticide penetration. They are also able to close down their respiratory system to avoid inhaling pesticides.
“Eliminating spiders from an area for a long period of time is almost impossible. Spiders do not congregate in a single large nest, so the population cannot be destroyed by targeting one site. New spiders will quickly recolonise an area if the inhabitants are killed off. In many species, young spiders (or ‘spiderlings’) disperse by ‘ballooning’. They spin silk strands that are taken by the wind, carrying the spiders over potentially long distances.”
The most effective way to prevent spiders from being in your house is to reduce their food supplies and minimise opportunities for them find shelter in dark places. Here are some tips on how to manage them:
- Install screens to keep out insects that are food for spiders
- Use yellow light globes externally so as not to attract insects to the house
- Fill cracks and crevices where you see webs inside and on verandahs and patios, and use draft excluders on doors and windows
- Vacuum into cracks and crevices and vacuum or use a cobweb broom to clear webs regularly
- To avoid spider bites: wear gloves in the garden; avoid leaving clothing on the floor, and check inside shoes before wearing
- For most spiders (other than redbacks), the “catch and release” method is the best way to remove them from your building. Simply take a piece of card large enough to cover a jar or container. Use the container to capture the spider, slide the card under the jar and carefully turn it over to form a lid. Carry the captured spider outside and release it in the garden.
- Care should be taken in sheds and spaces that have been left unattended for long periods as these are the most common areas that you may come across redback spiders
- Be sure to check for redback spiders inside hollow spaces of outdoor play equipment or areas where children play, especially in the warmer months from late September to April. You may need to use a torch.
- The best way to deal with a redback spider when found near a place where people live learn work or play is to kill it with the sole of your shoe, a rolled up newspaper, a vacuum cleaner, or use heat via a hair dryer, heat gun or a steam cleaner.
For infestations of areas like sheds, roof areas or spaces that can not be managed using the strategies above please contact us for advice about the safest treatment strategies.
- Department of Agriculture Garden Note “Common Spiders in our Neighbourhood” accessed 14 July 2017
- Isbister, G.K; Gray, M.R. 2003. White-tail spider bite: a prospective study of 130 definite bites by Lampona species. Medical Journal of Australia. 179. (4): 199-202.
- Gerozisis, Hadlington, Staunton, 2008: Urban Pest Management in Australia UNSW Press
Australian Museum website https://www.australianmuseum.net.au/spiders
Gerozisis, Hadlington, Staunton 2008 Urban Pest Management in Australia UNSW Press