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Fungus creates zombie beetles that crave flowers before death

Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world.

By Richa Malhotra

Species: Goldenrod soldier beetles (Chauliognathus pensylvanicus) Habitat: Meadows and fields on North America

Dying on a bed of flowers might seem like a good way to go. Except it’s not when you’re a beetle suffering a gruesome fungal infection.

Goldenrod soldier beetles (Chauliognathus pensylvanicus) feed and mate on flowers – and that’s where some of them meet their end, too. When infected with the fungus Eryniopsis lampyridarum, the beetles clamp their jaws onto a flower and die soon after.

Hours later and still stuck to the flowers, the dead beetles’ wings snap open as though ready to fly. With their wings raised, these beetles even attract mates – live males were seen having sex with zombie females.

“This would be like a person infected with a virus, who deliberately sought out a singles bar, grabbed hold of the bar with their teeth, and died there, where healthy humans would be exposed to infective virus particles,” says Donald Steinkraus at the University of Arkansas in Fayetteville.

He thinks this greatly increases the chance that the fungal infection will be picked up by healthy beetles. It attaches the infected beetles exactly where other healthy beetles are feeding and looking for mates.

Dramatic pose

Steinkraus and his team studied 446 live and dead solider beetles for signs of fungal infection. About 20 per cent of these were found to carry the fungus, with most of these assuming the same dramatic posture. They clung tightly to flowers using only their mandibles and their legs hung free.

But strangely, the wings opened only 15 to 22 hours after a beetle had died.

“If you went to a morgue where there was somebody that had been killed, and about 24 hours after their death they suddenly sat up or raised their arms, it would be very spooky,” says Steinkraus. That happens in these beetles and is done by the fungus, he adds.

The fungus becomes obvious in the post-death wing-opening phase, when its spores and filaments erupt from the beetle’s abdomen. Steinkraus says it is possible that raised wings and a swollen abdomen caused by fungal growth make the beetles look bigger, which may help attract a mate and spread the infection.

“Infected insects are known to adopt a number of unusual postures before and after death,” says Shelley Adamo at Dalhousie University in Halifax, Canada. “A good test to do in the future would be to glue the wings shut, as well as remove them altogether and test whether that affects infectivity.”

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