An inordinate fondness for beetles
Asked what a lifetime studying nature had taught him about the mind of its creator, the biologist J. B. S. Haldane is said to have replied that He appeared to have an inordinate fondness for beetles. The joke holds up. Around 400,000 species of BEETLE have been described — more than every kind of fish, bird, reptile, amphibian and mammal put together, several times over.
Insects as a whole account for roughly a million named species, which is over half of everything science has ever named, and the estimates of how many remain unnamed run into the millions. A jar from a single tropical tree can contain species nobody has ever recorded. The LADYBUG, WEEVIL and FIREFLY in this grid are all beetles, which is not obvious from looking at them.
Why there are no insects the size of a dog
An insect has no lungs and does not move oxygen around in its blood. Air enters through holes along its sides and travels down a branching network of tubes that deliver it directly to the tissues, which works beautifully — up to a point. Diffusion down a tube gets slower the longer the tube, so past a certain body size the middle of the animal simply cannot be supplied.
The ceiling moves if you change the air. During the Carboniferous, around 300 million years ago, oxygen made up roughly a third of the atmosphere rather than a fifth, and the fossil record from that period includes a DRAGONFLY relative with a wingspan of about 70 centimetres. When oxygen levels fell, the giants went with them. Everything in this grid is small because of the plumbing.
They were flying before anything else was
Insects got into the air something like 400 million years ago, well over 100 million years before the first bird, and for a very long stretch they had the sky entirely to themselves. Nothing could chase them, which is a considerable head start.
The DRAGONFLY still flies better than most things that followed. Its four wings are driven independently rather than in pairs, so it can hover, fly backwards, turn on the spot and pick a MOSQUITO out of the air mid-flight, catching its target on something like 95 per cent of attempts. A bird would be delighted with half that.
Six legs, three parts, and fewer of them every year
The test for a true insect is countable: six legs and a body in three sections. A spider fails on both. The grid holds the garden regulars — ANT, BEE, BEETLE and LADYBUG — the fliers BUTTERFLY, MOTH, WASP, HORNET and DRAGONFLY, the noisemakers CRICKET, GRASSHOPPER, LOCUST and CICADA, the small nuisances APHID, FLEA and MOSQUITO, the hidden TERMITE, WEEVIL and EARWIG, the praying MANTIS, the glowing FIREFLY and a CATERPILLAR partway through becoming something else.
They are also getting harder to find. German researchers who had been trapping flying insects in nature reserves the same way since 1989 found the total weight caught each summer had fallen by more than three-quarters by 2016 — in protected land, not farmland. Anyone old enough to remember scraping insects off a car windscreen after a long drive has noticed the same thing without measuring it.