These Ants Go Crazy For Eggs

Workers of the invasive yellow crazy ant species lay eggs that can serve as a source of food for the colony when times are tough.

AsianScientist (Jun. 6, 2017) – Scientists have revealed that for the invasive species of yellow crazy ant (Anoplolepis gracilipes), worker-laid eggs provide a valuable energy source for selected colony members. Their findings have been published in Frontiers in Zoology.

The yellow crazy ant is one of the world’s most ecosystem-devastating ant species, and is therefore also one of the most closely studied. Despite the scrutiny some of its basic characteristics, such how larvae are fed, have remained unknown.

In the present study, researchers describe how specialized ‘physogastric’ workers—with greatly-enlarged abdomens—produce two egg types: one for reproduction, and the other for nutrition. The latter variety, called ‘trophic’ eggs for their nutritional, non-reproductive role, were found to be the primary food source for larvae.

Additional observation revealed that these unfertilized eggs are also fed to queens and other castes in the colony as a supplement to their diets, confirming the role of physogastric workers as the ‘trophic egg chefs’ of the colony.

“This behavior may indicate adaptive advantages for this invasive species,” explained corresponding author Yang Chin-Cheng of Kyoto University. “Production of eggs by workers for food can help the colony overcome unfavorable conditions such as shortages.”

“Alternatively, if the queen dies or disappears, haploid males can be produced from reproductive eggs and then mated, offering an advantage for an orphaned colony.”

These revelations came as a surprise to the researchers, but also gave them hints for controlling infestations.

“We can now develop a strategy to combat this invasive species,” continued co-author Professor Lee Chow-Yang of Universiti Sains Malaysia. “For example, if we suppress the workers’ reproductive potential, it would cut off the nutrition supply for larvae and prevent colonies from growing.”

The team is considering, for example, incorporating a low concentration of hormonal analogue JHA as an active ingredient in bait used against yellow crazy ants, which they anticipate will produce the desired growth-limiting effect.


The article can be found at: Lee et al. (2017) Worker Reproduction of the Invasive Yellow Crazy Ant Anoplolepis gracilipes.

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Source: Kyoto University.
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