Why huge rafts of fire ants are floating around in Texan flood waters

Texans have an added reason to avoid floodwaters brought about by deadly Hurricane Harvey.

Fire ants.

The tiny creatures can bite and sting like crazy when touched, react en masse, and are notorious for being able to survive floods for weeks.

Now they have been spotted in waters around Houston.

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Fire ants uprooted by Harvey will cling to each other to make their slightly terrifying rafts. They are searching for dry land – be it a log, a house or even a person.

This is not something people want living in or near their house – even if flood waters mean they are temporarily evacuated.

The sting of a fire ant is characterised by an instant burning feeling which is accompanied by itching and a welt, according to the American Osteopathic College of Dermatology. After four to six hours they turn into a blister which lasts around a week. In the most severe cases anaphylaxis can occur.

Initially the rafts can look like heaps of dirt but on closer inspection they are moving and teeming with life.

A single fire ant is able to repel water but it’s only when they join together that they make air pockets to keep their water resistant colony raft afloat.

The structure of these fire ants rafts is so intriguing that engineers at the Georgia Institute of Technology have previously spent time studying them.

On average, each ant is connected to 4.8 neighbour ants. With legs, claws, mandibles and adhesive pads each ant has about 14 possible connections.

A CT scan of a frozen raft found that 99% of the ants had all available legs attached to other ants to bolster buoyancy. It also keep the strength of the raft intact through rough currents, such as those in Houston.

Smaller ants fill the gaps between larger ants so the raft maintains stability.

Fire ants originated from South America but have been in the US since at least 1918 and are considered a major pest.

The US Department of Agriculture says the insects have had an impact on agriculture and natural resources by “damaging crops, agricultural equipment, and impacting wildlife”.

To break up the rafts, people are advised to use washing-up liquid. The soap stops the ants from repelling water and making air pockets.