Sometimes you wonder what makes people tick. That companies want to grow at the expense of the future of the planet, food manufacturers use threatening language, or some endanger public health with their right to be antisocial, is difficult to understand. There are selfish motives at play. But it is less understandable that they are being held up over their heads.
Protecting someone else, even if it only has negative consequences for you and your offspring, some ladybugs do too. Often it is the seven-spot ladybug, Coccinella septempunctata, which may have the misfortune of being regarded as a suitable host. Or rather: hostess, because usually female specimens are the chosen one. Women have more substance. And more is better for the hungry larva of the wasp that has the scientific name Dinocampus coccinellae wears. This elegant animal with green eyes and long antennae doesn’t have a Dutch name, but that doesn’t stop her from flying around in search of a ladybug in which to lay an egg. The larva that crawls from it is initially very helpful. She eats any other parasites in the body. But then it’s done with good intentions and she starts on the hostess herself. She also avoids essential organs, because she likes to keep her meal alive. She will need it at a later stage. Instead, she consumes the beetle’s reproductive organs. The fat body is also fine, especially because it is constantly supplemented by the aphids that serve the ladybug as food, while it itself serves as food. Eat and be eaten.
Once fully grown, the larva squirms its way out. The victim is still alive, but cannot resist. When the wasp laid her egg, she also injected a virus that has now reached the beetle’s brain. That virus causes paralysis. The ladybug stands still, helpless, while the larva beneath her, anchoring its paralyzed legs, spins a flaxen, tawny cocoon. Inside it, the wasp undergoes its metamorphosis, while the victim holds her not only a hand above her head, but the whole body. Like a zombie, she stands there protecting her attacker. All she can move are her feelers—the short, antenna-like structures near the mouthparts. It will make them vibrate menacingly if an enemy of her enemy approaches.
Most ladybugs die when they have served their purpose as patroness. Yet a quarter manage to survive in the end. If the flaxen cocoon has been left and she manages to wrestle herself from it, such a hostess can simply continue feeding on aphids. Her offspring, however, have been made life impossible by the growing wasp. That is the thanks for protecting someone else.
We know what possesses the ladybug: a virus. But people who protect others who have a clear negative influence on the future?
A version of this article also appeared in NRC Handelsblad of 30 October 2021
A version of this article also appeared in NRC in the morning of October 30, 2021
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