Barry Warrington, from Hull Valley Wildlife Group, discovered a male and female long-winged conehead on a visit to Thorne Moors.
The bush-crickets are just 20mm in length and make their presence known by “stridulating”, rubbing their back legs together to produce a soft hissing, barely audible, buzz.
“I heard this faint noise,” said Barry. “They make a call to attract females which is a certain frequency which you can’t hear as you get to a certain age.
“Luckily I am still reasonably young.”
He returned a couple of days later with Yorkshire Orthoptera Recorder David Chesmore, armed with a bat detector to pick up the creatures’ faint calls. The discovery was confirmed by finding two further males.
When the species was first found in the UK in the 1940s, it was confined to the South Coast, but has been steadily advancing northwards. “It is most definitely a sign of a warming climate,” said Mr Warrington.
The adults die off as winter advances, with the eggs laid by the females emerging as nymphs the following summer.
All grass-hoppers and crickets stridulate – and some species can only be heard with a bat detector.