Ants float on a Harvey survival raft

Fire ants form a protective island as they float through the Houston flood.
Fire ants form a protective island as they float through the Houston flood.

HOUSTON residents were told to prepare themselves for the worst as ex-Hurricane Harvey smashed Texas, but there was one threat authorities didn't see coming.

Colonies of fire ants are banding together to form stinging horror rafts that have baffled locals affected by the category 4 storm.

The ants are an invasive species native to South America.

They have successfully colonised the southern US and form ant rafts when a major storm occurs, according to Science Alert.

The venomous insects quickly link together to escape floodwaters, putting their queen and larvae at the centre of the raft.

The ants then mesh together tightly enough that air is trapped in the middle.

The ants on the bottom are knitted so water can't get in.

The rafts can be large with more than 100,000 ants, according to one study.

The roles rotate with ants travelling across the top and joining the stationary layer on the bottom.

"We observed that ants would morph their raft into a pancake shape of two to three ant layers in thickness,” researchers said.

Ants travel atop the raft and join its edges.

Fire ants can survive in these structures for weeks or longer.

They constantly seek new dry land to colonise as they float.

Topics:  ex-hurricane harvey fire ant raft fire ants

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