Top left: Giant trapdoor spider Euoplos dignitas
Bottom left: European garden spider, Araneus diadematus
Top right: Gooty Sapphire Ornamental tarantula, Poecilotheria metallica
Bottom right: Banded Garden spider, Argiope trifasciata
Female house spider, Tegenaria domestica
Don't like spiders? Here are 10 reasons to change your mind
Back in the past, in what now seems like a lifetime ago, I managed the Emergency Operations Centre for my local Ambulance Service which was housed in a single-storey building in the grounds of the Church Hospital, Oxford. One of my nicknames was 'Spiderman' because of my fondness for spiders.
The roof space of this building was home to a population of 'house spider' or
Tegenaria domestica, a good-sized one of which can be 4 inches or more across its outstretched legs. They frequently paid us a visit by coming through the light fittings or round the edges of the aircon unit.
The house spider is well-named, being one of those commensal species that, like barn swallows, can't exist without human habitation and so must have evolved after we became settled and built permanent dwellings.
Despite its large fangs, it is entirely harmless to humans, even if it does manage to pierce the skin - something I tried to impress on my staff, whose first response to one running across the floor was to stamp on it.
Despite this reassurance, one of my assistants was so arachnophobic she refused to enter the room until the spider was gone - although what she thought it would do to her was a mystery, so one of my tasks was to gently catch the spider in my hands and put it outside, whereupon I would deliver my famous (or maybe infamous) spider talk, in which I explained why spiders are such fascinating creatures - their very long evolutionary history from a common ancestor with scorpions; their multiple eyes (some for binocular vision and some for detecting movement) and above all their amazingly engineered webs.
Orb web spiders like the common garden spider,
Araneus diadematus, make two sorts of silk - one to act as scaffolding and the radial threads of the web and sticky one to form the circular strands. Each thread of silk consists of multiple fine filaments that stretch very quickly to catch a flying insect without it bouncing off, then recoil slowly to avoid throwing the insect free. All this is controlled by the fine molecular structure and electrostatic bonds between the filaments. The result is a thread that, weight for weight, is stronger than steel.
One small spider that is common on walls and buildings in Oxford is the
zebra spider,
Salticus scenicus, a tiny black and white-striped spider, only a few millimeters long, that has amazing eyes. It is a hunting spider that preys on small insects, even some three times its size, by jumping on them. Its modus operandum is to crawl over the surface of walls and roofs and, when it sees its prey, it approaches slowly and when close enough, judges the distance perfectly and pounces. It will also jump across gaps, again with a perfectly judged jump, many times its own body length, rather like a human jumping the Grand Canyon from a standing start, but before it does so, it dabs the tip of its abdomen down to fix a 'safety line' of silk, just in case. To perform these feats, the zebra spider needs a high degree of visual acuity and binocular vison. The amazing thing about this spider is the way it overcomes the problem for visual acuity of such a small retina; it rapidly moves the retina up and down, effectively increasing its size.
The jump is accomplished, not by muscles in the legs, but by a sudden increase in haemocoelic blood pressure which straightens the front and back legs, so the spider always jumps with its legs extended.
I always hoped my spider talk would impress my staff enough to take an interest in spiders rather than seeing them as creepy-crawly things to be half-feared and killed simply for sharing the building with us. Alas, only one or two ever followed my example and picked them up to put them out of a window.
All that was by way of introduction to an article in
The Conversation in which Leanda Denise Mason, an Associate Lecturer, Curtin University, Australia give her ten reasons to like spiders, or at least change your mind it you don't. Her article is reprinted here under a Creative Commons licence, reformatted for stylistic consistency. The original can be read
here.