Why Do Wasps Taste Spice?

During the fall season in Kushihara, a mountain village in Japan, residents celebrate the seasonal eating of wasps. Wasp larvae, called manju, are boiled in soy sauce, sugar, and corn flour and eaten as a snack.

In Kushihara, which is located in Gifu prefecture, residents have traditionally relied on hunting and small-scale vegetable farming. In the past, wasps were considered a seasonal wild food. But today, many Japanese people fear eating insects.

It is not known why wasps eat spicy food. It is possible that they use it as a deterrent from wild animals. Capsaicin is a chemical found in chile peppers. It causes pain in neurons called nociceptors. When birds eat peppers, they do not experience the pain. However, mammals are sensitive to spicy food. In order to survive, animals must learn to tolerate plant defenses. The more an animal can tolerate plant defenses, the more food it can eat, and the more energy it has.

Researchers have found that tree shrews are more sensitive to capsaicin than mice. In fact, tree shrews have more genes for capsaicin than mice. The tree shrews prefer to eat plants that have capsaicin. However, it is possible that the tree shrews’ taste preferences are shaped by their environment.

The tree shrews prefer Piper plants. Piper boehmeriaefolium has a chemical called Cap2. Cap2 is chemically similar to capsaicin. The tree shrews’ taste preferences probably evolved due to their adaptations to their environment.

It is possible that wasps don’t like the scent of citrus fruits. However, the citrus fruit is a good deterrent for wasps.