Monday, 22 September 2014

THE FALSE WIDOW SPIDER


The false widow spider, Steatoda nobilis, is one of six noble spiders present in the UK. However the false widow is the only non-native member of the group, first entering the UK in the 1890s and is believed to have been imported from either the Canary Islands or Madeira.  It remained in one or two isolated spots until relatively recently but since the early 1990s it has been spreading across the south coast from the Bristol channel to the Wash.  The significant increase in their population during the last 25 years is believed to be due to the result of our warmer winters.

The false widow spider takes it name from its look-a-like cousin the deadly Black Widow spider, but that is where the similarities stop.  Steatoda nobilis have a bulbous abdomen which is usually dark brown with lighter brown marbling colours.  They have a distinctive cream 'skull' on their abdomen,  spindly red-orange legs and can grow up to 32 mm long. Their web is usually an irregular tangle of sticky fibres in appearance.

Like most native spiders in this group the false widow spider produces its egg sacs in the summer months. Females normally reproduce up to three sacs each year over their 4-5 year adult life span.  The spiderlings hatch within a month or so and then disperse using silk strand parachutes to be carried on air currents to a new habitat.  Spiderlings normally disperse either in late autumn or early spring, depending upon when their eggs were laid and the ambient conditions.

Although they are the most venomous spider in the UK, false widow spiders are not actually all that venomous. The physiological effects of a bite are similar to those of true widows but at a much lower intensity.  The bite from Steatoda Nobilis is similar to that of a bee sting and most people will only suffer localised pain and swelling.  However the bite may trigger in some an extreme allergic reaction called anaphylactic shock, which could prove fatal.

If you are bitten by a spider or stung/bitten by an insect then you must ensure that the wound does not get infected, by cleaning it with an antiseptic wash or soap and water as soon as possible. Placing a flannel or cloth soaked in cold water over the wound will help reduce any swelling. Avoid scratching the affected area to reduce the risk of infection. If there is a lot of swelling/blistering or there is pus in the wound this may indicate the wound has become infected. In that event you are advised to consult your local doctor.

There have been no fatalities from any spider bite in the UK, including the Noble False Widow Spider.  More severe symptoms are likely a result of an allergic reaction or subsequent infection of the wound and not all have been confirmed as bites from a noble false widow. If you experience any of the following symptoms as a result of a bite/sting then you are advised to call 999 and ask for an ambulance; wheezing or difficulty breathing; nausea, vomiting or diarrhoea; a fast heart rate; dizziness or feeling faint; difficulty swallowing; confusion, anxiety or agitation.

 Management

Most spiders are docile and even if they are capable of biting humans they generally avoid contact and move away at the first disturbance.  Bites normally only occur if a spider is extremely provoked, trapped under clothing or accidently squashed.  Spiders are generally not likely to be harmful unless accidently or deliberately molested.

Spiders of all types, native or exotic, can generally be maintained at manageable levels or even eliminated by simple housekeeping measures such as removal of webs and their contents at regular intervals and ensuring that all stored materials and equipment are cleaned and kept pest free on a regular basis. Regularly vacuuming or sweeping windows, corners of rooms, storage areas and other seldom used area helps remove spiders and their webs.  Vacuuming spiders can be an effective control technique because their soft bodies usually don’t survive this process.

One of the easiest ways to minimise encounters with false widow spiders is to reduce clutters around buildings, which derives them of places to make retreats.  However, it is impractical to eliminate them completely by removing all clutter.  In terms of avoidance of bites when cleaning areas simple precautions such as using gloves and coveralls, combined with vigilance to ensure spiders do not climb up garments, are normally sufficient.    Spiders can enter buildings through cracks and other openings. 

To prevent spiders from coming indoors seal cracks in the foundation and other parts of the building and gaps around windows and doors. Eliminate places for spiders to hide and build their webs by keeping the area next to the foundation free of rubbish, leaf litter and accumulations of other materials.  Removing ivy and other heavy vegetation growing around foundations and trimming plant growth away from buildings will discourage spiders, in general, from taking up residence near the structure and then moving inside. 

One aspect that makes controlling widow spiders difficult is that they. Like many spiders, exhibit and behaviour called ballooning.  When the spiderlings are very small on warm days when there is an updraft they climb to the top of a fence post of piece of vegetation, raise their abdomens into the air and release a small filament of silk.  When the updraft currents overtake the forces of gravity, the spiderling is carried into the air to another location.  This may only be a few feet away or it could be miles.  Ballooning spiderlings have been captured at 10,000 feet from the ground and 200 miles off shore.

Control 

Do not panic if you see a false widow spider.  If you are concerned by there presence you can remove them, but as a precaution not to handle the spider with your bare hands as the spider may bite in self-defence. If you, like me, are not brave enough to tackle a spider face to face then you can control them with a rolled up newspaper, slipper, vacuum cleaner or insecticidal aerosol spray. Large infestations can be treated by pest control companies.
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