Time, I think, for another extract from my new book, Ten Million Aliens

What does it mean, not a true spider? The phrase baffled me as a child. Anything that ran about on eight legs seemed to express a very clear truth, and not a terribly welcome one. The idea of animals being untrue raised a small turmoil in my mind whenever I came up against it. Seals, I remember reading, have sharp teeth and lived by catching and eating things, but they weren’t true carnivores (although of course they are now). Pandas, on the other hand, though they don’t touch meat in the normal way of things, are true carnivores, and still are.

There are an awful lot of species out there that look pretty much like spiders and which belong in the class of Arachnids, but are not spiders at all. There is a gulf between true spiders and untrue spiders. But the Arachnids also include quite a few species that don’t look anything like spiders: creatures that look as if they should be classified quite differently. They all fit into the sub-phylum of chelicerates, which includes arachnids, along with the smaller groups of horseshoe crabs and sea spiders – which, I should add, are not all that closely related to true spiders. The point to a zoologist is that they all share a one-piece head/thorax combination. I trust I make myself obscure. Perfectly? Then let us continue.

Some animals are capable of alarming you because they can kill you, others because they give you the creeps, still others because they make you jump. Mice and bats fall into the last category, but by far the best are the sun spiders or Solifugids. Not, of course, true spiders. They share a common ancestor with spiders but have diverged to form a separate group: I put that clarification in for my childhood self. One difference is that most spiders do a lot of hanging about. Solifugids don’t. As the sun goes down they get going. Instead of waiting to see what the world will bring them in the way of food, they set off at top speed until they bump into something edible. They tend to have a preferred sort of race-track, and they go round it again and again. They can reach speeds of 16 kph, 10 mph, which seems at least twice as fast in a confined space. When this space is somebody’s living-room and you’re sitting in it having a civilized conversation, this can be rather startling. Solifugids have a fine knack of making you think they have given up and gone away before reappearing at breakneck speed, making you – oh, all right, making me – emit a girlish squeak and pour a tablespoon or two of cold beer onto my crotch. They have a great nickname: the Kalahari Ferrari.

Harvestmen are disturbing in a quite different way: another group of Arachnids which doesn’t count as true spiders. They have incredibly long, thin legs, horrifyingly fragile things of cobweb thinness which support in the middle an unnaturally tiny body: or to be more accurate, an unnaturally tiny abdomen plus head/thorax combo. They appear over baths, looking horribly likely to fall apart and drop bits of themselves all over you… but perhaps I am telling you more about myself than harvestmen here. The arachnids comprise 650 families with around 65,000 described species. A lot of them are tiny, but still look pretty alarming under magnification. Mites are many and various, some feeders on detritus, some predators, some of them parasites. They include ticks, which feed on blood.

Scorpions are also arachnids. There is a glorious set-piece in one of Gerald Durrell’s books, in which Gerry’s brother Larry opens a match-box to light a cigarette and finds instead of matches a scorpion and young: “It’s that bloody boy… he’ll kill the lot of us… look at the table… knee-deep in scorpions…” Every morning when I am in the bush I bash out my boots before putting them on, to shake out the scorpions. I’ve never found one yet: not a detail that will ever stop me banging. There are a couple of thousand species of scorpions, and the champion is 20 cm, eight inches long. Don’t worry because my researches reveal the kindly fact that “only” 30 or 40 species carry venom strong enough to kill a human. Even scorpions are wary of scorpions. When they court, they seize each other by the pincers, so each can dissuade the other from turning an amorous encounter into a cannibalistic feast. When I was at primary school we were shown a Walt Disney film of this behaviour. It came, alas, with comic music, as if the scorpions were doing a silly dance to amuse humans: the darkened class-room was filled with silly glee. I still remember my hot-eyed fury at this. I couldn’t bear the thought that people thought animals silly. Surely if anyone was silly here, it was humans. No animal has been put on earth to amuse humans: to think so is demeaning to my family and to other animals. True spiders, untrue spiders and all their fellow-arachnids may give me the jumps, but that’s my folly and failure.