Locusts are known for their massive swarms, in which they devour crops and can destroy enough food to feed 35,000 people in one day. They are also cannibals, so huge swarms present a danger to the insects themselves – but researchers have found that migratory locusts produce a pheromone that throws their swarm-mates off their scent.

In the animal kingdom, cannibalism is pretty run-of-the-mill. “Not eating [members of your species] is a human invention,” says at the Max Planck Institute for Chemical Ecology in Germany. “It’s a loss of energy to not eat whatever is around.”

Recently, scientists determined that cannibalism helps drive locusts’ apocalyptic swarms. “They actually start eating each other from behind,” says Hansson. “You have to start moving, otherwise the guys from behind will eat you.”

Cannibalism even drives swarms in flightless juveniles, says at Max Planck Institute of Animal Behavior in Germany. “If swarms take flight they become even harder to control. It’s somewhat like a wildfire,” he says.

Hansson and his colleagues hypothesised that locusts must have evolved countermeasures to deter their neighbour from eating them when they gather in large groups. The researchers began by looking for odour compounds produced exclusively by juvenile locusts (Locusta migratoria) under crowded cage conditions of up to 250 individuals per cage. Using a technique called gas chromatography that separates out the different chemical compounds in a sample, they identified 17 compounds the locusts produced, including phenylacetonitrile (PAN). PAN was already known to deter other species such as birds, because it can be converted into a toxic cyanide compound.

To test if PAN protects against cannibalism in juvenile locusts, the researchers used CRISPR gene editing to create a line locusts that lacked the gene for PAN. These insects then quickly became the targets of cannibalism. In another line of locusts, the researchers disabled the olfactory receptor that detects PAN. This drove the locusts to begin eating any neighbour, even those producing the deterrent odour.

The findings could one day be used to help manage locust swarms, decreasing their numbers without need for current approaches like pesticides. at Texas A&M University says that in principle, blocking the locusts’ ability “to either produce or detect the pheromone has the potential to cause the locust populations to self-regulate by eating themselves”. It could also make locusts more vulnerable to other predators.

Zuul, destroyer of shins, was a living tank. This dinosaur’s spine and tail were covered in armoured plates studded with spikes, ending in a club previously thought to be used to fight off vicious predators like the Tyrannosaurus rex. But a rare fleshy fossil suggests these armoured herbivores probably used their tails less to fend off T. rex and more to dominate each other.

Zuul �����ܰ����������ٲ��ٴǰ�’s name comes from the demonic Zuul from the 1984 film Ghostbusters, with crurivastator meaning “destroyer of shins”. Its fossil was discovered nearly a decade ago – during a dig in Montana to unearth a Gorgosaurus, an earlier cousin of T. rex – when excavators bumped into the dinosaur’s tail club. Years later, when researchers at the Royal Ontario Museum in Toronto were preparing the fossil for exhibition, they found that some of the fossil’s spikes were damaged. Many of these had smooth areas indicating the bone had reformed, and some had growths of keratin – both signs of healing, suggesting injuries on multiple occasions.

“The [damaged spikes] are just in this little range around the hips, and just on the sides of the body,” says at the Royal BC Museum in British Columbia. They’re not broken on the top of the body or up by the head, which is where you’d expect a predator like T. rex to attack, she says.

“Big, predatory dinosaurs can bite with enough force to leave scratches and puncture marks on bone,” says Arbour. But these marks are missing on this fossil.

Based on the damaged spikes being at different stages of healing, and in a location both easily reachable by another Z. �����ܰ����������ٲ��ٴǰ�’s swinging tail and unlikely to be fatal, the researchers believe the dinosaurs used their tails to fight each other for social dominance. They suspect it was similar to the way modern animals use antlers or other body parts to stake claim to territory or mates. So, although the club-like tail may have come in handy for self-defence, its evolution was probably driven more by sexual selection than predation.

The idea of these dinosaurs using their tail clubs to fight off T. rex had “become something of a textbook stereotype”, says at the University of Birmingham in the UK. He sees this study as a prime example of how a long-standing hypothesis can be upended with new evidence. “Now that palaeontologists know what to look for, the same damage in other, maybe yet-undiscovered, fossils could come to light,” he says.

To escape sexual cannibalism, some animals move stealthily to avoid detection or even play dead – but male orb-weaving spiders have developed another approach: after copulation, they rapidly catapult to safety. This is the first time catapulting to avoid being eaten by a mate has been reported.

at Hubei University in China and his team first noticed this behaviour while studying orb-weaving spiders in the mountains in Wuhan in October 2019.

The researchers decided to investigate things further in the lab. They used high-speed cameras to capture the behaviour of 155 mating pairs of an orb-weaving spider (Philoponella prominens). Only three of the males didn’t catapult after mating, and all were promptly captured, killed and eaten by their partners. All of the males that catapulted after mating survived.

To further test the necessity of this behaviour, the researchers put a small paintbrush behind the spiders that blocked the males from catapulting. They, too, were all killed and eaten.

The cameras revealed that the males launch themselves at remarkable speeds of up to 88.2 centimetres per second, which Zhang says is impressive for a spider only around 3 millimetres in length. That is as if a person 183 centimetres tall flung themselves 538 metres – the length of about five football fields – in 1 second.

at the State University of New York at Fredonia says this research contributes to our understanding of how sexually cannibalistic species continue to successfully mate. But he wonders if the escape strategy might also be used in response to other threats. “Have males co-opted a general anti-predator defence or is this uniquely an adaptation to reduce the risk of sexual cannibalism?”

Zhang and colleagues hypothesise that this behaviour evolved to signal fitness as mates. “If a male could not catapult, or the catapulting ability is not good, the female may deplete or eliminate its sperm, and accept other males’ courtship and sperm,” says Zhang.

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