When a scorpion meets a scorpion

Waltzing scorpions, frying grasshoppers and the disappearance of the locusts are among the treats that await the reader in three new nature books. Tim Flannery reviews these books which will reawaken our interest in the natural wonders of the worldThe Smaller Majority: The Hidden World of the Animals That Dominate the Tropics by Piotr Naskrecki. Belknap Press/Harvard University Press, 278 pages, €29
and
Locust: The Devastating Rise and Mysterious Disappearance of the Insect That Shaped the American Frontier by Jeffrey A. Lockwood. Basic Books, 294 pages, €20.75

The invention of the microscope revealed wonders to the world, and permitted Jonathan Swift to quip:
So, naturalists observe, a flea
Hath smaller fleas that on him prey
And these have smaller still to bite ‘em
And so proceed ad infinitum.
By the late 20th century, fascination with the minuscule had begun to pall, and now it takes an exceptional book indeed to reawaken our interest. Thankfully, in David Attenborough's Life in the Undergrowth, Piotr Naskrecki's The Smaller Majority and Jeffrey Lockwood's Locust we find three works that do so.
Life in the Undergrowth is Attenborough's tribute to the terrestrial invertebrates, so diverse that they make up most of the species on Earth. They are, he says, a group of creatures that make life possible for us – whether as scavengers, aerators of soil or agents of pollination – to name only three of their functions. As he succinctly puts it, “We are greatly prejudiced by our size.”
The book commences with the descendants of the first creatures to clamber out of the water and onto land – the scorpions and their relatives. They made the transition some 400 million years ago, long before plants or our ancestors left the oceans.
If you have never thought of scorpions as remarkable, Attenborough advises that you try to pick one up, perhaps with a pair of very long forceps. Whichever method you use it will not be easy, for scorpions possess advance warning systems that sense where you are and what you are doing.
Their six pairs of eyes are strategically positioned so as to leave no blind spot, and while lacking sharp focus they are capable of detecting the tiniest variations in brightness – and thus movement. Yet they cannot be dazzled because each one has its own built-in “sunglasses”, composed of pigment granules, which cover the lens as light increases. Before it sees you a scorpion will either have “heard” you through the minute hairs on its claws, or detected your advance through a slit-shaped organ on the upper part of each leg, which is so sensitive to vibration that it can pinpoint the footfall of a beetle a yard away. Or perhaps it will have detected you with its pectines. These comb-like organs have no parallel among other living creatures. They are packed with nerve endings and are probably capable of smelling or tasting minute traces of chemical compounds in the ground over which the scorpion passes.
When a male scorpion meets a female scorpion, his mind is very much on the ground under his feet. You can tell this from his pectines, which scan the earth while he shakes his body back and forth. He then approaches the female and stings her on the soft flesh in the joints of a pincer. This seems to relax her, allowing him to grasp her claw in claw, bring her face to face, and begin a scorpion waltz. In the laboratory, scorpion pairs have waltzed for two days. But in nature half an hour or so seems to suffice, with the dance terminating when the male locates a really choice piece of ground (the long laboratory waltz may occur because the male cannot find the right type of ground).
Soil texture is important in scorpion sex because instead of a penis males have a detachable spike which must be firmly implanted in the ground if insemination is to occur. Once the spike is in place the male manoeuvres his partner so that her genitals are atop it. As the spike bends under her weight two tiny valves open, through which the sperm is released.
Human beings need an ultraviolet light to see scorpions at night, because that light makes their bright green fluorescence visible to us. But other night creatures may be able to detect the fluorescence unaided. These superb adaptations have been honed by 400 million years of evolutionary experience during which countless billions of individual scorpions with blind spots, less sensitive pectines, or poor fluorescence have been weeded out, until finally we are left with the seemingly perfect, yet utterly alien, creatures here described.
Piotr Naskrecki has traveled the world with his camera, seeking out rare and little-known creatures, and The Smaller Majority is a book filled with some of the most beautiful wildlife photographs I have ever seen. He does not restrict himself to terrestrial invertebrates, but includes some smaller vertebrates such as lizards and amphibians.
Naskrecki's own speciality is the study of grasshoppers, to which he devotes a dozen or so pages. Some particularly vivid species are found in Australia, as is a locust troublesome to farmers, and Naskrecki has spent considerable time in the Australian outback documenting these creatures.
Locusts, according to Jeffrey Lockwood's excellent book Locust, are simply grasshoppers with peculiar habits. There are ten species worldwide, and they are characterised by their roving swarms, which can appear out of nowhere and can devastate crops over a considerable area. Each continent has its own locusts, and each species has evolved independently from less troublesome grasshopper relatives.
The Rocky Mountain locust – the sole species recorded from North America, and now thought of as extinct – was the most numerous and devastating of them all. Throughout the 1870s, military posts across the American frontier dispatched reports on the devastation left by the locust swarms. Each tells only a local story, but when they are put together the extent of the destruction becomes clear. Then, in the closing decades of the 19th century, the locust swarms stopped coming. Just ten years after their final sighting, an entomologist working in Russia made a remarkable discovery that threw just about everything entomologists thought they knew about locusts into disarray.
Boris Petrovich Uvarov was studying Locusta danica, a bright green, solitary creature that causes no harm to farmers. If their density increases, however, the next generation becomes black and red, long-winged, and prone to travel long distances. What he had discovered was not evolutionary change but something very different, which came to be known as the theory of phases. Uvarov discovered that the smell of grasshopper faeces, and the frequent disturbance of the tiny hairs on the grasshopper's hind legs caused by crowding together with other grasshoppers, were the key cues leading to transformation. And he discovered that the changes were entirely reversible. When the numbers dropped, the next generation would develop into solitary, green grasshoppers.
This remarkable discovery opened the possibility that the Rocky Mountain locust may not be extinct after all: Perhaps it, too, had phases, and its solitary phase was still lurking somewhere in the West, awaiting the conditions needed to spark its transformation. The theory had many powerful adherents.
Then, in the late 1950s, a study of male grasshopper genitalia provided a definitive answer to the riddle. Grasshopper phalluses are precise tools. Each species has its own shape, and each will fit only into a female of the same species. Study of the seventeen Rocky Mountain locusts preserved in museum collections revealed that their phalluses were unique. Thus they were not a phase of another species.
Some thought that the spread of alfalfa, which disagreed with the locust's digestion, might have caused its disappearance. Others felt that the demise of the buffalo was somehow involved. Jeffrey Lockwood, however, had his own ideas. He figured that the outbreaks had to come from somewhere and that if the cradle of the Rocky Mountain locust swarm could be identified, then so would the cause of the creature's extinction.
The swarms, he established, originated in the high valleys of the Rockies. The species probably required just 3,000 square miles as its nursery, and may actually have used far less.
At around the time the locust vanished, the high valleys were being settled. Grazing, irrigating and cropping, it seems, transformed the vital nurseries in ways that made them inhospitable to locusts. Thus a few farmers banished from the land a creature that once rivalled or even exceeded the passenger pigeon in abundance, and which had threatened farming across a vast region.
At the very end of his fascinating book Lockwood takes us to Yellowstone National Park, whose fertile valleys were set aside as a reserve in 1872. The park had acted as a last refuge for the buffalo, and Lockwood wondered whether the locust might have survived there also.
“I think I know who they were,” Lockwood confides, “so I released them back into the field. Because I did not remove them from the park, their identities and location need not be reported to the authorities”. Perhaps echoes of the frontier will once again be seen.
© The New York Review of Books