An Arizona man landed in hospital with severe bruises, welts and swelling on his arm after he was bitten by a mystery insect.

Thomas Jay said he was taking out the trash from his home in Chandler, Ariz., approximately 40 km southeast of of Phoenix, when an insect he’d never seen before bit him. Within hours, the round bite started to swell and multiple dark, painful bruises spread across his left arm.

“The bite itself was a circular bite and it already had like a white, sealed skin on top of it,” Jay told local TV station CBS 5.

His wife, Dee Petrov, shared the incident on the Living Chandler Facebook page and quickly got responses from dozens of people urging Jay to see a doctor immediately. 

“We had 100 people (who) right away said don’t joke around, this is serious,” Petrov said.

Within a 24-hour period, Jay was transported from an urgent care centre to two different hospitals, where doctors and toxicologists were stumped, the couple said.

Jay’s arm was covered in dark purple bruises and no one was sure how to treat him. Because doctors didn’t know what bit Jay, they decided to err on the side of caution and just take biopsies and blood samples while monitoring his condition.

The couple says the insect that bit Jay resembled a solifugae, an arachnid also known as a camel spider or wind scorpion, but they can’t be sure.

Nearly two weeks later, Jay’s arm is showing some improvement, but he’s still suffering from the bite.

“There’s still excruciating pain that’s in the arm and it moves from different places at different times,” he said.

Petrov has started a Go Fund Me page to help cover her husband’s medical bills. She said any leftover money will be donated to “research and education in hopes that we can help better fight these types of medical emergencies.”