DNA analysis by Kobe University reveals edible wasps feed on 324 species including vertebrates

DNA analysis of the diet of the wasp species Vespula shidai, one of the ingredients used in "hachinoko" (bee larvae), a local insect cuisine from Nagano and Gifu prefectures, has revealed that the wasps feed on 324 species, including vertebrates such as birds and mammals in addition to insects and spiders, according to research by Kobe University and others. This validates the appropriateness of experienced beekeepers who have provided diverse feeds including vertebrates based on observational knowledge, offering insights into the relationship between food culture and nature.

In the Chubu region, including Nagano and Gifu Prefectures, there is a culture of eating the larvae and pupae of wasps such as the Asian yellowjacket wasp, as well as locusts, aquatic insects called zazamushi, and silkworm pupae as protein sources. Hachinoko is also known as a delicacy, and enthusiasts collect nests from the wild, provide feed to grow the colonies larger, and then consume them. However, when it came to their diet, only general knowledge from old surveys and literary works indicated that they ate insects, spiders, and frogs, with no detailed understanding.

Assistant Professor Tatsuya Saga studies ecology at the Graduate School of Human Development and Environment of Kobe University and has been researching wasps since his student days. He decided to investigate what the wasps had eaten using "DNA metabarcoding," which reads organism-specific DNA sequences like barcodes from intestinal contents, as databases of DNA information for various organisms have been developed.

Saga and his colleagues targeted the edible Vespula shidai in the satoyama (traditional rural landscapes) of the Chubu region, collecting 20 and 32 larvae respectively from 5 wild nests and 7 reared nests in Gifu and Nagano Prefectures. When they opened the abdomens of these larvae to separate undigested material from the intestines and analyzed DNA gene sequences, they found a total of 324 species used as food, including insects such as moths and stink bugs, spiders, birds including crow family members, mammals, as well as amphibians, reptiles, and fish.

The number of food species was almost the same between wild and reared nests, but more vertebrates were detected in the wild nests, indicating they were feeding on carcasses. In the reared nests, DNA from chickens, deer, and quail that had been provided as feed was detected at high frequency.

Some kind of bird DNA was detected from all nests, and mammalian DNA was detected from almost all wild and reared nests, indicating that birds and mammals are important food sources for V. shidai. The practice of enthusiasts providing bird and mammal meat when rearing these wasps overlaps with wild food selection, demonstrating that the experiential knowledge of wasp keeping is scientifically valid.

The research was conducted with Assistant Professor Haruna Fujioka of the Graduate School of Environmental and Life Science at Okayama University and was published in the electronic version of Journal of Insects as Food and Feed, international journal, on May 14.