Spiders are not everyone’s brownie in a mug, more often they are deemed hairy, scary and relegated to a life beneath a glass on your bathroom floor. The media are not particularly supportive of these fascinating animals either. Cases of spider bite deaths (confirmed or otherwise suspected) always receive a lot of attention and the media like to proclaim that there are many more that go unreported.
In the UK almost a third of women and a fifth of men are thought to experience general anxiety around spiders. In fact arachnophobia is thought to be the most common animal related phobia. Then again how often do you encounter a shark in your back garden? Investigations into what causes arachnophobia and the evolutionary and behavioural mechanisms concerning it are prevalent. It has been shown for example that despite an individuals judgement of a spider to have low harmfulness they may still give it a high fear rating, possible evidence of irrationality. Furthermore if you compare spiders to bees and wasps you cannot explain the fear in terms of objective risk, spiders are still feared much more frequently. Perhaps this is related to our ancient hunter-gatherer society’s long affinity with bees for their honey. Humans therefore have a longer history of experiencing being stung by bees and know it is not that harmful (at least to a non-allergic). Spiders on the other hand, encountered much less frequently, had bites that were not necessarily well known. There is a benefit to approaching a bee nest but no obvious advantage for doing the same with a spider, thus a lack of experience persists through the generations and myths are formed. This process may be the cause of fear in later generations (Gerdes, et al., 2009).
Even in current times the clinical effects of bites by important spider groups (common or well known groups) have not been well documented. Fears may persist because of this or they could be entirely unfounded, especially considering injuries can be caused by other organisms but misattributed to spiders.
For instance in a study of 750 definitive spider bites in Australia none of them caused a hypersensitive reaction (as a bee sting would) and there was only evidence of an allergic response following contact with the body hairs of a spider (usually causing mild irritation). In the same study the longest period of pain after a spider bite was 48hrs with many lasting less than 3hrs. The majority of the 6% of medically significant bites were caused by the Australian redback spider and the duration of pain was only 24hrs or longer because the patients were not given antivenom or did not seek appropriate medical attention. Two of the largest studies concerning suspected spider bites revealed that around 80% of cases were related to other organisms altogether (Isbister and Gray, 2002).
Nonetheless, in the near future, with appropriate clinical research into the effects of spider bites and increased public awareness of their effects (therefore seeking appropriate medical attention) this type of accidental injury will become much less common. I refer to it as an accidental injury because as mentioned previously the spider will only bite as a last resort or if it feels threatened (for instance if you step on it in your shoe). Spider venom after all has not evolved to harm large vertebrates as say a wasp’s has to defend its colony against a hungry bear. So the spider has no reason to assume biting will be any more beneficial than simply running away.
- Gerdes, A., Uhl, G., and Alpers, G. W. (2009). Spiders are special: fear and disgust evoked by pictures of arthropods. Evolution and Human Behavior, 30(1), 66-73.
- Isbister, G. K., and Gray, M. R. (2002). A prospective study of 750 definite spider bites, with expert spider identification. QJM, 95(11), 723-731.