ARE SPIDERS DANGEROUS?

Whilst not quite as badly maligned as snakes, spiders also tend to take the rap for many things they don’t do.

So in order to try and help their cause a bit, and hopefully provide HO’s with some useful facts, Astri Leroy  has kindly given us permission to serialize her  updated publication “ARE SPIDERS DANGEROUS” which we will do over the next four  weeks.

But first – who is Astri Leroy?

Her Linkedin profile is long enough to post as an article on its own, so here are just a few snippets from it.

  • Started The Spider Club of Southern Africa in 1975 with 5 other individuals and currently Chairman. Since then have been a major mover in the club which attempts to bridge the gap between hobbyists, amateurs and the professional scientists.
  • Wrote “Spiderwatch in Southern Africa” which was revised and updated to be published as “Spiders of Southern Africa”. These books were illustrated by my husband John Leroy’s photographs. Both were published by Struik and the latter is now available as an e-book.
  • Co-authored several scientific papers on spider behaviour and checklists of spiders for some of the S.A National Parks.
  • Compiled a checklist of the arachnids at the Walter Sisulu National Botanical Garden.
  • Member of The International Society of Arachnolgy, The American Arachnological Society, British Arachnological Society and of a founder member of AFRAS the African Arachnological Society.
  • Specialties: Citizen Scientist in Arachnology, specializing in spiders (Araneae).

PLEASE NOTE: All photographs in the booklet are copyright John Leroy.

So without any further ado

Part 1

ARE SPIDERS DANGEROUS?

By Astri Leroy

with help from Prof Gert Muller

 

 

Introducing spiders

Spiders are small land-based predators with 8 jointed legs, external skeletons, two main body parts, simple eyes, no wings or antennae. They lay eggs but do not metamorphose.  All spiders produce silk and many build beautiful webs.

They are probably the most abundant land-based predators and although insects are the primary prey, some can catch small birds, mammals, reptiles, amphibians and even fish.

Southern Africa with its varied topography, vegetation types and habitats from deserts to forests, mountains to wide grassy plains, man-altered landscapes and wilderness areas – has a huge number and diversity of these little predators. They range in size from the comparatively gigantic baboon spiders or “African Tarantulas” to adult spiders with body length of less than a millimetre. The majority are modest-sized, inoffensive and keep to themselves. There’s at least one and probably more not very far from you now. Don’t run away spiders are not aggressive- they’re not out to get you. So the answer to “Are spiders dangerous?” is generally “No”.

VENOM 

All spiders produce venom, except members of one small family, the Uloboridae.  Spider venom is a mixture of saliva, venom and digestive fluids, used to subdue, kill and digest their prey – usually invertebrates.  In general it has little effect on large mammals, including people. A bite may hurt at first, can itch for several days but if left to subside without being scratched will disappear with no lasting ill effects. Venom does not persist in the body and the effects of a bite will not recur later. Spiders will only bite if squashed against our skin – they don’t even bite in self-defence as some larger creatures do.  They do not make a living from sucking our blood and are not vectors of any human diseases. They cannot lay eggs under our skin and won’t make nests in our hair.   In fact they will avoid contact with big, dangerous creatures like us at all costs. This means that spider bites are uncommon and the effect venom of most spiders on humans is unknown because they simply don’t and often cannot bite us.

There are however a very small number of species in only three of the 71 families of spiders that occur in South Africa that DO have venom of medical significance and these are the spiders shown in this booklet. (We have more than 2200 species of spiders in South Africa).

Next week  – SPIDERS WITH MEDICALLY SIGNIFICANT VENOM – Button or Widow spiders

 

 

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