The hornets that attacked three people in Loire yesterday (August 21) were most likely disturbed by something in the surrounding environment, three experts have told The Connexion.
The attack happened in the morning in a wood near Briennon, a village of 1,700 people to the north of Roanne. Three cyclists from a group of 10 were swarmed by hornets while on a mountain bike ride in the area.
Two people were stung around 50 times each and were admitted to intensive care, while another sustained 15 stings.
Experts say the attack could have been triggered by noise from a nearby vehicle, fear that the nearby cyclists would pose a threat to the nest as they had touched it or come very close or stress caused by the recent heatwave.
Another theory is that the wind may have dislodged their nest and the hornets felt under threat.
The three experts believe that the hornets involved are of European origin, as the location of the nest was in a dead tree stump, an environment more common to European than Asian hornets.
The Service départemental d’incendie et de secours Loire has now confirmed this and say they are 100% sure the attack involved European hornets.
“The attack must have been sparked by cyclists having touched the dead stump,” said Étienne Roumailhac, owner of the wasp nest eradication firm LGF (Landes guêpes frelons) and a prominent figure of the industry.
Mr Roumailhac published a video about the incident on his personal Youtube page, which is followed by more than 446,000 subscribers, exploring different theories about the cause of the attack.
Matthieu Bonnemaison, another pest control technician and owner of Roussillon Guêpes-Frelons, said that the hornets could have been disturbed by agricultural machinery passing by, for example.
“With such a massive attack, cyclists must have rested or cycled at a moderate pace nearby,” said Eric Darrouzet, a research scientist at the University of Tours and a hornet expert.
Mr Darrouzet also suggested that climatic conditions – the recent heatwave and storms – as factors which could have led to the attack.
No way to prevent hornet attacks
All three experts said the only possibility of avoiding an attack is to pay close attention to the possible presence of hornets, by looking around in spots where they could set up a nest such as canopies, tree stumps, garages or sheds.
Hornets choose such locations during the summer because they shelter them from the outside to avoid heat and to protect themselves from wind or other animals’ attack.
European hornets typically choose cavities during winter before moving outside during the summer while it is more random for Asian hornets, which is one of the reasons why it was hard at first to give an absolute definitive answer on the species involved in Sunday’s attack.
The experts did not recommend installing bottles as traps as this harms biodiversity by capturing thousands of other insects.
Instead, they recommended a specific trap designed specifically for hornets that is shaped like a square with an inverted bottleneck to release smaller insects and keep hornets inside.
Are hornet-related incidents becoming more common?
The experts disagreed on whether hornet attacks were becoming more or less common.
Mr Roumailhac said three quarters of the responses he was given from professionals report less hornets this summer, while Mr Darrouzet said it varies from region to region.
“This is the first time in ten years that I am observing such a sharp decrease in hornet activity,” said Mr Roumailhac.
Mr Bonnemaison – who is based in the Pyrénées-Orientales region – said he had carried out more nest-removal calls but added that this could be due to his firm being more visible on search engines rather than an increase in the hornet population.
Professionals in the Normandy region confirmed to The Connexion to be concerned heavily by the phenomenon.
But Mr Roumailhac said he found that he was being called to more incidents regarding established nests, which suggested that people were simply waiting longer before reporting the issue.
“I am surprised that there have not been more accidents, to be honest,” he said.