Spiders in New Zealand – Types, Bites, Control & Prevention

  • Spiders are not insects! Spiders have eight legs, insects have six. They belong to the Class Arachnids, which includes scorpions, mites and ticks.
  • There are more than 45,000 species around the world, coming in all shapes and sizes. However, only a handful of these species are common in and around homes.
  • Generally speaking, from a pest control point of view, spiders are considered as beneficial, as they help keep genuine pests in check. However, spiders are still one of the top pests for homeowners – certainly they are frightening for arachnophobes, but they create messy webs and some do indeed have dangerous bites.
  • From an identification and pest control point of view it can be useful to classify spiders into web-building species and ground dwelling or running species.

 

Perhaps the top two spiders of concern for homeowners are the redback and the white tail. Due to their painful bites most homeowners, especially those with children and pets, will take action if they see a either of these species.

Other than the redback, the most common species around buildings is probably the black house spider. Although it can give a bit of a painful bite, it is considered more of a pest due to the dense webs it can build around doors and windows, and under eaves.

Perhaps the scariest spider, even for non-arachnophobes, is the huntsman. Due to its size and speed, and habit of ‘jumping’, it’s certainly a spider to get the pulse racing!

Apart from the obvious species, such as the redback and white-tail, identifying spiders for non-experts can be a bit tricky.

For help in working out what type of spider you may be looking at, apart from the images above, check out our guide for help with spider identification.

 

Most species have a similar life-cycle;

  • The male – often a lot smaller than the female – goes looking for a mate
  • The mating ritual can be quite lengthy and elaborate
  • After mating the male will often be eaten by the female or die
  • The female lays her eggs in an egg sac;
  • The young spiders (spiderlings) that hatch are miniature versions of the adult

Life span of adult females is generally around three years, although in captivity they can live much longer.

Spider eggs

Spiders lay their eggs in a protective silk egg sac. This provides protection against the environment and some (but not all) predators.

The placement of these egg sacs vary between species; some keep them in the web (black house), some hide them (orb weavers), some protect them (huntsman) and some even carry them until they hatch (wolf spiders).

Baby spiders

Baby spiders are more accurately called spiderlings. After hatching from their egg they remain inside the egg sac until their first moult (they moult as they grow).

Once outside the egg sac, the spiderlings will remain close by for a while before they disperse. Some spiderlings disperse by ballooning – climbing to a high point and dropping a silk line to catch the wind and taking off. Spiderlings may be carried up to several kilometres by this technique.

Wolf spiders are known to care for their babies after hatching, with the spiderlings remaining with the mother, hitching a ride on her back for several months until their fat reserves have been used up and they need to start finding their own food.

 

Most spiders spin silk egg sacs to protect their eggs and often the female will either carry the egg case or stand guard nearby to protect them.

Learn more about the spider egg sacs of the common Australian species.

 

Spider webs (cobwebs) are made out of a proteinaceous silk. It is produced from spinnerets at the end of the abdomen and it’s an amazing material – it has a tensile strength far greater than steel of the same weight, and with greater elasticity.

Webs come in various shapes and sizes. In addition to the traditional radial web (orb weavers), there are ‘funnel’ shaped webs (black house and funnel-webs), more irregular three dimensional ‘nets’ (redbacks) and sheet webs.

Although some species do not build webs, they can still produce silk, sometime to wrap prey once caught and females also use silk to build egg cases.

There is also the bolas group of spiders that spin a line of silk with a sticky blob of silk at the end, which they use to “lasso” moths as they fly by.

If you were ever wondering whether spiders can stick to their own web… they can! They have dense hairs and non-stick surface on the surface of their legs and avoid getting trapped by spinning the web very carefully. They actually produce two different types of silk – structural silk (which they walk on) and sticky silk (which is used to catch the prey).

 

Funnel-webs can be fatal and if you get bitten you need to get immediate medical treatment.

It can be difficult to tell the difference between a funnel-web, mouse spider or even black house spider, so if you have been bitten by any black spider with a body length greater than 2 cm and you are unable to identify the species, it is recommended you should follow the first aid procedure for a funnel web bite:

  • Keep the victim still and calm
  • Call an ambulance
  • Apply a pressure bandage covering the effected limb continuing above the bite site
  • DO NOT use a tourniquet, cut, suck or wash the bite site
  • If possible, take a photo of the spider for identification

The good news is that there have been no fatalities from a funnel-web bite since the anti-venom was developed in 1981.

A number of other common spiders will give a painful bite: the redback, black house and white-tailed. The redback is considered the most toxic and can cause nausea, general pain and sweating and so is more likely to require medical treatment.

The general treatment for a spider bite (other than the funnel web and similar black spiders) is:

  • Apply a cold compress or ice pack to the bite site for 20 minutes
  • DO NOT APPLY an immobilisation bandage
  • An antihistamine applied as a tablet or cream can be applied to prevent itching
  • If in doubt get medical attention.

Sometimes victims can suffer a severe allergic reaction to a bite resulting in anaphylactic shock. Should the victim develop swelling away from the bite site and / or difficulty in breathing seek medical help immediately.

Does the white tail spider cause flesh to decay?

Although there have been reports of necrosis / gangrene resulting from a white tailed spider bite, these have not be supported scientifically.  In cases where this has occurred, it is more likely from a post-bite infection (possibly from excessive scratching). The venom itself has no necrotic properties.

 

For homeowners, killing a single spider, especially of a web-building species, is relatively straight forward – just spray the spider with a spider spray or crawling insect aerosol. But if you have a particular problem or want lasting protection, it’s probably best to call a professional pest manager with their experience and specialist products.

Professional spider treatments

The type of treatment a professional pest manager will provide will depending on the species present.

Web-building spider treatment

Often web-building spiders will be included in a general pest treatment, as the pest managers will treat the perimeter of the building and other pest hotspots where web-building species tend to build their webs. However, they can do a specific treatment for redbacks and other web-building species if there is a specific problem or infestation. Due to the behaviour of web-building species and the effectiveness of the treatments, it is not uncommon for pest managers to offer a 6 month warranty / service-free period and sometimes longer.

For DIYers or even professionals, the use of a broom to brush down cobwebs is a very useful control tool.

Treatment for running / hunting spiders

Treating for running / hunting species is a bit more problematic. Such spiders tend to be nomadic and so it is always possible a stray individual will come wandering in from surrounding areas in search of shelter and food. They can walk across treated zones on the tips of their legs and as such will often pick up insufficient amounts of insecticide. However, a comprehensive general pest / perimeter treatment will eliminate other pests which are the main food source for hunting spiders. As a result your home will be far less attractive to these species and the chances of them coming in will drop off dramatically.

Sometimes the problem is not just an occasional spider, but an infestation! This would mean there must be ideal breeding conditions in or around the property. In such circumstances the pest manager will do an inspection to try and locate the hot spots. This may result in specific treatments in roof voids and wall voids, or in the case of funnel webs, treating an area on the property where spiders have been located.

For more information on professional treatments, check out our magazine articles:

Different spiders, different treatments

Common spiders – identification and treatments

 

  • Get regular professional pest sprays to eliminate insects that are the main food source for spiders
  • Keeping garden beds away from the edge of the house will significantly reduce the spider population
  • If garden beds next to the house are kept in place it is important to keep vegetation trimmed back from the edge of the house and paths
  • Avoid having plants at head height either side of a path to avoid webs being built across paths
  • Keep clothes, shoes and sheets off the floor to reduce spider hiding places – huntsman, white tails and funnel-webs all like hiding in small, tight places

 

Check out our library for a range of articles on pest control spiders.