Federal and state investigators said on Wednesday that a dead male hornet was retrieved after a Marysville resident reported it on 4 June to the state Department of Agriculture.
“The find is perplexing because it is too early for a male to emerge,” said Dr Osama El-Lissy, deputy administrator for the US Department of Agriculture’s quarantine programme.
Entomologists believe the recent find maybe an old hornet from a previous season that wasn’t discovered until now as males don’t usually emerge until July.
The intimidating insect's measure at 2in (5cm), is the world’s largest species of hornet and is a threat to honeybees and native hornet species.
These insects are known to brutally attack hives, swiftly destroying the structure and decapitating bees in what scientists call the “slaughter phase”.
The hornets are not particularly aggressive toward humans, but their repeated stings can also be fatal and are extremely painful.
Entomologists from the state and US Agriculture departments said it’s the first confirmed report from Snohomish County.
Mr El-Lissy said that the federal agency would work with state officials “to survey the area to verify whether a population exists” in the county.
Sven Spichiger, an entomologist with the state Agriculture Department, said they will “now be setting traps in the area and encouraging citizen scientists to trap in Snohomish and King counties”.
The hornet was submitted to the federal Animal and Plant Health Inspection Service for final verification and DNA testing showed that the bug was unrelated to other hornets in Whatcom County or Canada.
“This new report continues to underscore how important public reporting is for all suspected invasive species, but especially Asian giant hornet,” Mr Spichiger said.
He added: “None of this would have happened without an alert resident taking the time to snap a photo and submit a report.”