What are Japanese wasp larvae really eating? Hundreds of species identified

Larvae of the wasp species Vespula shidai are considered a delicacy in central Japan. Known as hachinoko, the larvae are either harvested from wild nests or reared by hand in rural woodlands.

But until recently, little was known about what these larvae actually eat – especially when comparing their diet in the wild to those reared by humans. A new study from Kobe University has taken a closer look – literally – at the gut contents of these larvae.

Using DNA metabarcoding, a genetic method that can detect multiple species from a single sample, researchers found that wild colonies of these wasps feed on a far wider variety of animals than previously reported.

The findings reveal more than just dietary preferences – they open up conversations about biodiversity, flavor, and the future of sustainable wasp farming.

The wasp’s gut tells a story

The researchers examined larvae from both wild and human-reared nests. The team was led by Tatsuya Saga, an entomologist at Kobe University, who was inspired by a rather vivid personal experience.

“The research idea was inspired by my firsthand experience of eating the larvae of the giant hornet without removing the intestines and seeing that the intestines are filled with various creatures. As the beetle fragments jiggled in the mouth, I thought that examining the intestines will reveal what the wasps are eating,” said Saga.

DNA metabarcoding identified a stunning 324 different prey species in the wasp larvae. These included not only insects and arachnids, but also birds, mammals, reptiles, amphibians, and even fish.

Most nests showed a heavy dietary focus on birds and mammals, but wild nests contained a significantly greater variety of vertebrate species.

Wild wasps taste better

The differences didn’t stop at biodiversity. It seems that the diet of the larvae affected their flavor when eaten.

The researchers distributed a questionnaire to consumers of hachinoko, especially those with rearing experience. Of those surveyed, 58% said they could taste the difference between wild and reared larvae – and most preferred the wild kind for its richer flavor and aroma.

This sensory difference hints at a more complex relationship between what the larvae eat and their appeal to human consumers.

Still, larvae from both wild and reared nests showed high levels of captured insects. This suggests that even under rearing conditions, V. shidai wasps maintain their potential to help control insect populations.

However, the reduced reliance on vertebrate carrion in reared nests could eventually change the way carrion decomposes in local ecosystems, potentially affecting scavengers and nutrient cycles.

Balancing culture and sustainability

“In recent years, food products based on indicators such as low environmental impact and high production efficiency have been the focus of attention,” said Saga. “But I was made keenly aware once again of the value of a culture in which humans have lived in and interacted with nature and fed on its creatures.”

That balance – between ecological mindfulness and cultural heritage – is at the heart of this study. It highlights the importance of supporting traditional practices while ensuring sustainability.

By understanding what these wasps are eating, we can develop smarter, more ecologically informed rearing methods.

That said, the researchers caution that their study was limited to autumn and a relatively small number of nests.

To gain a full picture, future studies should explore different regions, seasons, and cultural factors that influence feeding and flavor.

As with many traditional foods, understanding the biology behind the taste can help preserve and adapt culinary heritage for future generations.

The future of wasp rearing

As interest in edible insects grows worldwide, understanding the feeding behavior of species like Vespula shidai becomes more important.

The recent findings on wasp larvae diets open up opportunities to refine rearing practices so they align with both ecological needs and cultural values.

By adjusting feeding methods to better reflect natural diets, it may be possible to improve not only the nutritional quality but also the taste of reared hachinoko.

At the same time, researchers emphasize the need for expanded studies. These should examine wasp behavior across different regions, seasons, and cultural contexts. This will help guide sustainable management strategies that are rooted in both science and tradition.

With better knowledge of what wasps eat and why it matters, the path forward combines biology, ecology, and culinary heritage in a uniquely Japanese way.

The full study was published in the journal Journal of Insects as Food and Feed.

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