Fire ant predation on eggs

Predation on eggs of Pomacea canaliculata
by the fire ant Solenopsis geminata

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The ant Solenopsis geminata
The fire ant Solenopsis geminata (Fabricius, 1804) lives in large colonies. They prefer a sunny and open habitat, eventually partly shaded. Their nests are mostly build in drier parts of the area, although occasionally, they inhabit wet places as well.
The colony of the fire ant consist of 3 types of ants: the queen, the soldiers and the minor workers. The queen produces the eggs and lives deep inside the nest. She is fed and taken care of by the workers. She is also the founder of the colony. The large (3-5mm) and robust soldiers or major workers defend the colony and assist the minor workers in carrying food to the nest. The major workers are distinguished from the minor workers by their square sheped head with strong, powerful mandibles (jaws). The minor workers, which are a bit smaller than the major workers, do most of the daily work: they collect the food, maintain the nest, take care of the larvea and the queen.
During warm months, new queens and male ants appear from the eggs and shortly thereafter they leave the nest. These male and female ants posses wings and after leaving the colony, the only thing they do is mate. The male ants die, while the females look for a good place to start a new colony.

Marisa eggs
Solenopsis geminata: Major worker.

Source images: Japanese Ant Color Image Database
(pictures not licenced under creative commons)

Marisa eggs
Marisa eggs

The name 'fire ant'
The common name 'fire ant' is used for many species of ants of the genus Solenopsis. This is not without reason, as their stings cause an intense, burning pain. When the fire ant stings, she actually damages the skin and sprays an aggresive fluid under the skin. Each ant is capable to sting several times. Immediately after the sting has been administered, an intense pain starts and a red wheal is formed. In the next 12-24 hours, the area swells and starts to itch. After a week, the wheal dissapears and a smooth, pink area is left on the skin. During the weeks thereafter, this pink spot diminishes and eventually a scar is left.

Feeding
Solenopsis geminata is not particularly selective in its feeding pattern. These scavenging ants feed on grass seeds, arthropods, sweets, meats and whatever they can obtain and digest. They also tend honeydew producing mealybugs, which they protect against predators, in turn for the honeydew. This latter feeding behaviour has a negative effect on agriculture, as the mealybugs are a pest itself and are know to spread plant diseases.

Distribution over the world
The fire ant Solenopsis geminata is indigenous to Central America, with its most northern distribution being the Southern regions of the USA.
Human transport of goods around the world allowed this fire ant species to become distributed accross tropical and sub-tropical regions of various continents. The ant became established in Africa during the first decades of the 20the century. It was, for example, observed in Gabon in 1914. The ant became distributed to Asia as well and was reported to occur in Thailand (1997) and the Philippines (1998).

Fire ants on eggs
Fire ants (Solenopsis geminata) on the egg mass of Pomacea canaliculata. Click on picture to enlarge.
(picture not licenced under creative commons)

Solenopsis geminata predating on Pomacea canaliculata egg clutches.
Solenopsis geminata has been observed to eat the eggs of Pomacea canaliculata in both the Philippines and Thailand. This is quite remarkable as almost no other animal is known to predate on the eggs of this snail, despite their conspicuous red colour. The eggs of Pomacea canaliculata are considered to be unpalatable. The ants damage egg clutches and transport the eggs one by one to their nest. Of they cannot capture the complete eggs, they destroy the eggs capsule and collect the yolk and the embryo. Eggs of different stages of development are attacked. The ants make no difference between fresh and hatching clutches.

The fire ant as biological control agent
The use of biological methods to control snail populations is gaining more and more attention. The observation of the fire ant Solenopsis geminata predating on the eggs of the apple snail Pomacea canaliculata suggest a possible role for this ant as a biological agent for the apple snail pest.
To achieve satisfying results in terms of snail population control with this ant, a large number of ants should be able to enter the rice field. Therefore, irrigation and drainage have to be adapted to allow the ants to reach the apple snail eggs. It's also important to provide a suitable habitat for the ants to build their nests (dry places).
Cautions should be taken as the fire ant can establish as a pest itself. They can have a very negative impact on the local ecology, as they predate on many species. The ants are also known to damage irrigation tubes, in which they chew holes. Also, one should be ware of another downside of these ants: their tendency to sting people.
It(s hard to predict if the ant Solenopsis geminata will ever be used as biological agent to control the population of the pest snail Pomacea canaliculata on a large scale. Taking in account the positive and negative aspects this ant might be used in an integrated management strategy in those areas were the ant Solenopsis geminata is already established.

References

Acknowledgements
I wish to thank Yoichi Yusa for providing information (see article above), his assistance, and the beautiful photograph of fire ants predating on the eggs of Pomacea canaliculata.


Related: 'Pest Alert' section, 'ecology' section and 'Asian distribution map' section.

 

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