The red imported fire ants (Solenopsis invicta) are remarkable insects that can create complex structures out of their own bodies without relying on centralized coordination.
When a colony of fire ants gets flooded, they form to create a raft, keeping the queen and eggs, larvae, and pupae high and dry in the middle. Thanks to their exoskeleton that repels water, and also to their hairs that trap water bubbles, even those workers that form the bottom layer are safe from getting completely submerged. But they are not safe from predators. Fish may eat some of them as they float - and they can float for up to two weeks - so if the colony doesn't reach dry land soon enough, the raft may collapse.
It takes about 100-120 seconds for the ants to form the raft, and millions of them can be aboard. They hold onto each other with their sticky feet and mouth parts - an individual can have as many as 20 other ants grabbing its legs and feet. By grabbing an ant's limbs rather than its body, the raft may change shape more easily, and other ants may join the raft more quickly.
The show is over as soon as you spray some soap on them, since soap lowers the surface tension of water, and the raft will immediately sink, leaving no more floating islands of fire.
The ants are South American natives, and have invaded countries such as the USA or Taiwan where they are invasive species.
Photo credit: National Park Service (source)
Common name: | Red imported fire ant |
Scientific name: | Solenopsis invicta |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Hymenoptera |
Family: | Formicidae |
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