Among the most thought-provoking of such creatures are the ranchers. These ants carefully tend herds of sap-sucking aphids, tiny pear-shaped insects, which they milk for a sugary substance that makes good ant food. Just like human farmers, the ants ensure that their herds get the best possible forage. They do this by driving their aphids to parts of the plant that are rich in sap, and when the aphids produce young (which are miniature versions of the adults), the ants carry them to fresh pastures.Flannery also has a section asking why the locust, which used to dominate the Midwest—one swarm that rolled into Nebraska in 1875 and ate up all the crops, paint, window blinds, wooden tool handles, dead bats, and live birds it could find numbered some 3.5 trillion insects—is now almost completely extinct. No one really knows why; maybe they're hiding, maybe all the locusts turned into grasshoppers (yeah, I don't really understand that part either), or maybe the Mormons asked for divine protection. Or:
Ant shepherds drive off aphid predators such as ladybirds, and in bad weather build shelters of leaf particles and soil to protect their livestock. They have even been observed marking their herds with a substance specific to one ant colony; it resembles our branding of livestock, Attenborough says. But most astonishingly, the ants have discovered how to interfere with the reproduction of their herds so as to maximize production; just as we castrate calves, so the ants feed their aphids a fluid which prevents them from reaching sexual maturity.
Jeffrey Lockwood, however, had his own ideas. He figured that the outbreaks had to come from somewhere and that if the cradle of the swarm could be identified, then so would the cause of the creature's extinction.Here's another good review of the Jeffrey Lockwood's Locust, which also describes some of the inventions frontier farmers came up with to stave off the swarms, including a "horse-drawn flamethrower" that, apparently, never made it past prototype.
The swarms, he established, originated in the high valleys of the Rocky Mountains. The species probably required just three thousand 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 rivaled or even exceeded the passenger pigeon in abundance, and which had threatened farming across a vast region.