They Can Be Cannibals

Color variation in Asian ladybeetles (photo from Wikimedia Commons)

While writing about the worldwide spread of Asian ladybeetles (Establishing a Bridgehead) I learned another amazing fact. These insects are cannibals when they need to be, but they’re careful about it. They avoid eating close relatives.

Asian ladybeetles (Harmonia axyridis) are insect carnivores, preferring aphids above all else. Their population surges when aphids are plentiful and goes hungry when aphids crash. Rather than starve, ladybeetle larvae eat eggs and smaller larvae of their own species. The strong ones survive, indirectly regulating their own population.

However, they also make sure that their own family survives …

Interestingly, H. axyridis recognize their kin and are less likely to cannibalize a sibling than a non-related individual (Michaud, 2003). If normal prey becomes scarce, larval mortality can be very high, with in excess of 95% of larvae failing to survive to adulthood, and in such circumstances cannibalism can be essential for survival.

— Invasive Species Compendium, Harmonia axyridis

I’m not surprised that they eat each other, but I’m amazed that they recognize their relatives and avoid eating them.

(photo from Wikimedia Commons; click on the caption to see the original)

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