Arachnida Araneida

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Spiders can be a major cause for concern as venomous bites may cause injury, serious bodily harm and even death. Some people are severely allergic to spider bites and may go into anaphylactic shock, which can be lethal. In New Zealand, particularly venomous spiders include the Katipo (Latrodectus katipo) and the Redback Spider (Latrodectus hasselti). Other spiders of concern include the White-tailed Spiders (Lampona cylindrata and L. murina). Spider webs can also be an unsightly annoyance around the home and garden.

Given the nuisance and potential risk to human health, it is important to control, prevent and monitor for spiders in and around the home.

Best Treatment for Spiders

To control spiders in the home spray Blitzem! Outdoor/Indoor Barrier Spray Ready to Use which is a low toxicity product but a highly effective combination of surface spray insecticides. Kill spiders and other insects on contact and provides barrier control for up to 3 months in and around the house. Spray surfaces of walls, cupboards, behind sinks and other fittings and especially into cracks and crevices of: walls, fences, up under the eaves, around door ways, around window frames, along skirting boards, ceilings, along cornices, cupboards, behind sinks and other fittings. Do not apply to fabric.  

  • Once spiders have been detected, treat at the earliest sign of infestation when populations are smaller and much easier to control.
  • Use other registered pesticides to control pests and remove spiders’ food source on indoor plants such as aphids, caterpillars, fungus gnats, mealy bug, mites, whitefly and various other common motile pests of indoor plants.
  • Control pests inside the home such as bed bugs, cockroaches, fleas, flies, moths, mosquitoes and various other common motile pests of indoor areas.
  • Regularly vacuum around the corner of rooms and brush or dust the corners of the ceiling to remove any webs.

First Aid:

  • In the event of a bite or suspected bite, seek medical advice urgently – call TRIPLE ONE (111).
  • Elderly, sick, immunocompromised, children and pregnant women are most at risk from spider bites.
  • First aid training is useful for anyone to have, especially if you or someone you know is at a high risk of spider and snake bites.  
  • If you are unsure which spider has bitten the patient, or unsure if the spider which has bitten is dangerous, call TRIPLE ONE (111) immediately.
  • If safe to do so, take a photo of the spider which has caused the bite.
  • Make note of identifying features of the spider including size, colour and patterns.
  • Check the spider has gone and will not return to bite.
  • Do not leave the patient alone.
  • Do not move the patient and keep the patient as still as possible.
  • Keep the patient calm and reassured.
  • Spider bite treatment varies according to species and as such, we recommend seeking further medical advice.

What are Spiders and how to get rid of them

Description:

Not all spiders are dangerous, most are harmless and quite beautiful. For example, Peacock Spiders are brightly coloured and patterned and perform an elaborate choreographed mating dance. Spiders are also an important part of the ecosystem and help to control garden pests.

Spiders come in a vast array of colours, patterns, shapes and sizes. The largest spider in the world is the Goliath Bird-Eating Spider from South American, with a leg-span of 28 cm.

The head and middle section (thorax) are fused (cephalothorax). At the front of the head region are four pairs of eyes. At the front and underside of the head are a pair of arm-like appendages (Chelicerae) which attach to the fangs. Fangs are generally used for piercing prey and injecting venom. Venom may be used for killing or immobilising prey, and may also liquify the body for later feeding. Another way of liquifying is to spit digestive enzymes on to their prey. Further outwards from the chelicerae are a pair of small antennae-like appendages (pedipalps), used for holding and helping to manoeuvre prey while feeding. On the underside of the cephalothorax are four pairs of legs. Spiders do not have antennae and are wingless.

The rear section (abdomen) is soft and rounded. At the tip of the abdomen are a pair of short appendages (spinnerets) which are used in producing silk. Silk is manufactured inside the abdomen from specialised silk glands. Silk is a sticky, strong and flexible substance which is used for various functions including building cocoons; nests; webs for catching prey; and wrapping their prey. Webs can be spun in a variety of patterns and forms according to the function of the design.

Lifecycle:

After mating, the female spider spins a cocoon-egg-sac in which the fertilised eggs are placed. Females may lay a few eggs or many hundreds of eggs at a time. Females may leave once eggs have been fertilised or may stay until eggs have hatched. Some females place the egg sac on their backs and carry it around with them.

Eggs may hatch with a few weeks or after many months. After hatching, juvenile spiders (spiderlings) emerge from the egg sac. Spiderlings are similar in appearance to adults, only smaller. Some species carry their spiderlings on their backs. Some spiderlings will run away after hatching while others will ‘fly’ away using single strands of silk elevated and transported by the wind. Spiderlings grow through many stages, shedding skin (moults) at each stage. At full maturity, adults are ready to mate and reproduce. Spiders live for various lengths of time. The longest-lived spider on record, aged 43, is the Australian Trapdoor Spider.

Habitat:

Many species are night dwelling and hide throughout the day. Many ground dwelling species move about after heavy rain or landscaping, for example. Some species wander during the mating season, generally during summer and autumn. Spiders are mostly active during the warmer months and in periods of high humidity.

Spiders primarily feed on other animals (carnivory) such as insects, other spiders, fish, frogs, snakes, lizards, birds and small mammals. However, some spiders may feed on the nectar from flowers.

Outdoors spiders can be found:

  • Underneath pots, bird baths, boulders and pavers
  • Inside fencing
  • Up around the eaves
  • Along the edges of windows and doors
  • Near drainpipes
  • Underneath the house
  • In crawl spaces
  • Underneath logs and dense shrubs
  • In trees

Inside the home, spiders can be found near the corners and crevices of a room including:

  • Ceilings and cornice
  • Along skirting boards
  • Around window and door frames
  • Underneath furniture
  • In fabric items after being brought indoors, accidentally
  • Indoor plants

Natural Enemies

Ticks, centipedes, other spiders, parasitic wasps, amphibians, reptiles, birds, mammals and even humans. 

 

Symptoms of Spider damage

Evidence of spiders may include:

  • Living or dead adult and juvenile (spiderling) spiders. Spiders which have been squashed may causes staining to fabric or light-coloured hard surfaces such as the ceiling.
  • Webbing - often in the upper corners of the roof, under the eaves, around window and door frames and along fences.
  • Cocoons or egg sacs
  • Faeces - may vary in colour but is generally black, grey or brown, which smears on to surfaces due to their mostly liquid diet. Faeces can stain surfaces.
  • The cast skins (moults) of spiderlings and adults.

Medical symptoms: 

Depending on the spider’s species, sex, individual, environment and intensity of bite; and also the patient’s age, health status and susceptibility, symptoms of spider bite may include:

  • Death
  • Sweating
  • Weakness, muscle pain and cramping
  • Headache
  • Nausea
  • Vomiting
  • Fever
  • Chills
  • High blood pressure
  • Swollen glands
  • Anxiety
  • Difficulty breathing
  • Anaphylaxis

At the site of spider bite, symptoms may be:

  • Swelling
  • Welts
  • Redness
  • Pain
  • Rash
  • Blisters
  • Some may cause secondary infection
  • Ulceration 

How to Prevent Spiders Appearing

Prevent from Spiders entering the home:

  • Avoid leaving shoes, clothing, towels, bedding, toys and other items outside the home. Spiders can crawl into these items and be brought back into the house inadvertently.
  • Reduce entry points to buildings: repair holes, cracks and gaps in walls, skirting boards, windows and doors.
  • Ensure flyscreens are fitted and maintained.
  • If possible, cover vents with a fine mesh.
  • Install a door seal or door snake to the bottom of entrance doors.
  • Keep doors closed at all times.
  • Avoid using outdoor lighting at night as this attracts insects toward the house, which in turn attracts spiders.

Reduce the environment favourable to Spiders:

  • Some spiders are attracted to other spiders, ensure webs are removed regularly from in and around the home and spiders are controlled.
  • Keep other pests out of the home.

Exclude Spiders from vulnerable items:

  • For items that must be left outside such as sports gear (helmets, gloves, shoes, etc.), place items in a secure plastic container.
  • For easy to move outdoor furniture, store indoors when not in use.

How to avoid being bitten by a spider:

  • Wear gloves and closed-toe shoes while gardening
  • Always check underneath furniture prior to placing hands underneath, or sitting legs underneath.
  • When moving pots, bird baths, boulders, pavers and other items spiders can hide underneath, carefully lever the item away from you first, then quickly check underneath for spiders.
  • Avoid going into the garden at night when spiders are more active and not easily seen.
  • Check lawn, outdoor and indoor areas prior to use, especially for children.

Monitor:

  • Be extra vigilant of wandering ground-dwelling spiders after periods of wet weather; after landscaping/digging; and during summer.
  • Check in the corners of rooms for evidence of spiders and control as soon as spiders are identified.
  • Check underneath outdoor furniture.

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