Crazy Ants strike again

The residents of Mare Anglaise and La Batie have been calling to say they have been invaded by fourmi maldiv. This is the latest of reports received every so often of population explosions of these insects known as crazy ants in English.

The crazy ant was first reported in the Seychelles in 1969 at Maldives on Mahe, hence their Creole name. Soon they became a huge problem and spread to other areas. The ants invaded homes, crawled over people’s food, entered ears, nose, eyes and open wounds. They killed new born chicks, pigs, dogs, cats and rabbits, and were the indirect cause of damage to important crops.

Bird Island was invaded by the ants in 1997-1998, and they spread to 90% of the island. In the area the ants occupied, they killed land crabs, insects, made the sooty terns fail to nest, and many of the Seychelles skinks disappeared.  A research study by Nature Seychelles showed that the ants, by farming scale insects on trees, almost destroyed the Mapou forest on the island

They may first occur in and around houses, nesting in cracks in the walls or other moist areas nearby.  The name crazy ant comes from frantic movements and frequent changes in direction, especially when they are disturbed. They can spray an acid liquid towards their prey and also towards humans if they get disturbed, which irritates the skin and will attract more ants.

A nest can have on average 40 queens, and a total of 4000 ants. The crazy ants can create “super-colonies” where queens and workers in different nests cooperate. No one knows what makes the crazy ants suddenly multiply and create super- colonies. They were present on Bird island before they became a problem.

Crazy ants farm scale insects from which they get food.  Scale insects suck sap from plants and therefore damage the plants they infest. They secrete sugary liquid called honeydew, which the ants like.  The ants protect the scale insects. In turn, the ants are allowed to collect drops of honeydew that these insects secrete. Some of the honeydew will also fall on the leaves and make fungus grow that damages the trees.

These ants are listed as one of the 100 most invasive species in the world. Known as “tramp species” they are carried in all manner of ways throughout the world. They cause problems wherever they occur.  On Christmas island where they almost destroyed the red crabs, they are now under control. In Seychelles, insecticides used ranged from the now banned Aldrin to slow acting bait like Fipronil.and the faster acting Cypermethrine. But longer-term control has to be something other than dangerous pesticides.


by Nirmal Jivan Shah, Nature Seychelles' CEO, on the People Articles, January 26th 2006.

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