Stinging caterpillars are invading Paris only weeks after a panic over bedbugs.

Pine processionary caterpillars – whose name refers to how they travel in single file – have arrived three months earlier than usual because of unusually mild temperatures, experts say.

Entire neighbourhoods have reportedly been taken over by the insects that measure up to 0.4 inches (4 centimetres) in length, live in groups and weave silk nests in the colonised pine and oak trees.

While the insects do not bite, their hairs are like “microscopic needles or harpoons” that detach from the caterpillars’ body when they feel threatened and travel with the wind, says the French health and safety agency ANSES.

The hairs contain a toxic protein that can cause blisters on the skin and a variety of allergic reactions.

The caterpillars and their hairs can also be fatal for pets and toddlers who may inadvertently put them in their mouths.

In 2022, processionary caterpillars were designated by the government as harmful to human health.

After finding huge colonies of caterpillars nesting in his 15-metre-high pine tree, one homeowner in the northern department of Yveline was forced to cut down the tree he had planted 20 years ago.

“I couldn’t believe it,” Emmanuel told Le Parisien. “They came down from my pine despite the trap I set. They are devouring my tree and I am afraid for my dog.”

In the final larval stages, pine processionary caterpillars descend along the trunk to bury themselves in the ground and transform into a chrysalis.

“It’s an invasion,” Jean-Marc Pommier, the mayor of Bonnières-sur-Seine, told Le Parisien.

“People are calling the town hall. We have entire neighbourhoods affected, we see trees covered with these horrible garlands (sic).”

The caterpillar invasion follows a major bedbug scare that made locals and tourists alike skittish about travelling throughout the city.

France’s tourism minister Olivia Grégoire is on two-day trip to China to try and woo Chinese visitors, particularly affluent tourists, back to France.

Despite the reopening of Chinese borders a year ago, visitor numbers from the nation have dwindled. In the pre-Covid year 2019, Chinese tourists represented 3 per cent of foreign tourist visits, but 7 per cent of tourist spending equal to €3.5 billion (£3 billion).