An invasive Asian hornet, which preys to honeybees, has been identified in Lancashire, officials said.
The insect, which is smaller than the UK's native hornet, was spotted by a member of the public in Bury, in a cauliflower that was found to have been grown in Boston, Lincolnshire.
The Asian hornet poses no greater threat to human health than a bee, but they prey on important pollinating insects such as honey bees and could do serious damage to colonies here, which have not evolved to cope with the threat.
Asian hornets arrived in France in 2004 and are now common across large areas of Europe, with experts on standby in the UK in recent years for the insect's arrival here.
Work is under way in both Bury and Boston to identify any nests, including setting up a surveillance zone and traps in the two locations, and deploying bee inspectors to visit local beekeepers, the Environment Department (Defra) said.
It is the first confirmed sighting since last year, when a nest was discovered in Woolacombe in North Devon and destroyed, while the first sighting on the UK mainland was in Gloucestershire in 2016.
Nicola Spence, Defra deputy director for Plant and Bee Health, said: "While the Asian Hornet poses no greater risk to human health than a bee, we recognise the damage they can cause to honey bee colonies.
"That's why we are taking swift and robust action to locate and investigate any nests in the Bury and Boston areas following this confirmed sighting.
"Following the successful containment of the Asian hornet incursion in North Devon last year, we have a well-established protocol in place to eradicate them and control any potential spread.
"We remain vigilant across the country, working closely with the National Bee Unit and their nationwide network of bee inspectors."