1,400 species found in guts of Asian hornets

University of Exeter researchers tested Asian hornet samples from France, Spain, Jersey and the UK throughout the hornet's active season.

Eaten prey included a wide range of bees, wasps, flies, beetles, butterflies, moths and spiders.

Although the European honey bee was the most common species found in the hornets -- appearing in all sampled nests and almost all larvae within those nests -- their diet is a lot broader.

An invasive species, Asian hornets are now found in much of western Europe. Nests are destroyed in the UK mainland each year as authorities try to keep the species out.

"Asian hornets are known to prey on honey bees, but until now the full range of their diet hasn't been tested," said lead author Siffreya Pedersen.

"The diet varied strongly over the seasons and between regions, showing that they are highly flexible predators.

"Most insect populations are in decline due to factors such as habitat destruction and chemical pollution. The expanding area inhabited by Asian hornets poses an extra threat."

The study used a method called deep sequencing to identify prey species in the guts of more than 1,500 Asian hornet larvae, which eat food provided by adult hornets.

Of the top 50 invertebrate prey species identified, 43 are known to visit flowers -- and among these were Europe's three main crop pollinators: the European honey bee, the buff-tailed bumblebee and the red-tailed bumblebee.

"Insects play vital roles in enabling ecosystems to function -- including pollination, decomposition and pest control," Pedersen said.

"Our study provides important additional evidence of the threat posed by Asian hornets as they spread across Europe," said Dr Peter Kennedy, from Exeter's Environment and Sustainability Institute.

The researchers identified 1,449 "operational taxonomic units" in the guts of hornet larvae. More than half could be identified as specific species, but the rest could not -- so the exact number of species found in the samples is not certain.

The research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and the British Beekeepers Association.

Samples used in the study were provided by the Jersey Asian Hornet Group, INRAe, the University of Vigo and DEFRA.