By Francesco Tomasinelli

Updated 2/3/2007

Each spring new alarm calls warn about the danger of Arthopods bites and spiders and their kin are the most targeted. The vast majority of spider bites cause only mild or no reactions. But in recent summers sack spiders were particularly active in Europe; many bites were reported and some patient even hospitalized. Surprisingly the European Arachnids fauna is pretty diverse, especially in southern countries, and the sac spider is by far not the worst of all.

According to every scientific paper treating spiders of medical importance the European black widow, Latrodectus tredecimguttatus, is the most dangerous species in our continent. They are native to France, Italy, nearby islands and Spain, and are closely related with tropical and semi-tropical widows like Latrodectus mactans. Adult female can measure 15 mm in body length while male are much smaller and completely harmless. Black widows have one of the most potent venom among animals but this is injected in very small quantities, leading to a very limited number of casualties (< 5%). These spiders are not even aggressive and the European species do not live in close proximity of humans.
The already mentioned yellow sack spider, Cheirachanthium punctorium, is for sure responsible of many more bites. This is a medium sized spiders (less than 20 mm body), with a bad attitude living in grassland and gardens. The venom have mostly local effects but sometimes can cause limited necrosis.
Probably the European violin or recluse spider, Loxosceles rufescens, related to much more dangerous american L. reclusa and L. laeta can be considered more threatening than previous genus. Loxosceles are pretty small, with red-brown bodies less than 10 mm long in adult females and a little less in males. The bite can produce swelling and necrosis and on very rare occasion this can lead to kidney insufficiency and clotting alternation that can persist for several days, leading to death. In year 2000, in the city of Milan, an italian woman succumbed to a probable poisoning by Loxosceles, biting her two times on the neck. The symptoms  developed in the worst way and the woman deceased after 3 days.
Others Arachnids, like the hobo spider, Tegenaria agrestis, has a bad reputation but bites are very rare and so is for Steatoda paykulliana and Steatoda grossa, less dangerous relatives of the black widows.  The big famous European tarantula, Lycosa tarantula (photo story and info here) and relatives from Southern Europe, are sometimes credited to be very poisonous. But actually it’s almost always Latrodectus tredecimguttatus, living in the same areas, responsible of serious poisoning  and the almost harmless L. tarentula is claimed guilty because of its size and fast moves.
The other hundreds of European spiders species pose really no threat to humans with the biggest species causing nothing more that a wasp sting.
Among the scorpions only Buthus occitanus has a powerful sting, a big Arachnids reaching 6-8 cm in total length, but his distribution is limited to Southern Spain, France and Portugal. The much more common and widespread European scorpion Euscorpius sp. are almost harmless.

Despite the very limited danger they pose spiders are among the least liked of all animals. On the contrary arachnophobia, or fear of spider, is the most common of animal phobias. A survey in United Kingdom states that nearly 50% of woman and 10% of men admitted to some degree of arachnophobia when questioned. About 3% of people claimed an extreme fear, and the most people claimed some apprehension. In many cases the problem can be solved taking confidence with the animals thanks to specialized personnel that helps the patient to understand that most Arachnids do not pose any threat.

See Surprising spiders for a wide portrait of this group of Arachnids.

Many thanks to Emilio Scoti, Stefano Verzura, Fabio De Vita, Manuel Mariotti, Francesca Pantaleoni