Two of the UK's nocturnal creatures are "in crisis", say conservation groups, who are asking the public to take part in a national survey.
Butterfly Conservation and the Bat Conservation Trust are asking people to take part in a "National Moth Night" on 15 May to find out more about the creatures and their habitats.
They say UK moth numbers have fallen by a third in the past 40 years.
This poses a threat to the bats that feed on them.
There are now 17 species of bat in the UK, all of which are protected by law because their numbers have decreased so dramatically.
The groups hope that the night-time event will draw attention to the creatures' plight and shed light on the threats they face.
Richard Fox, surveys manager at Butterfly Conservation, said: "We need to learn as much as we can about which moths are facing the biggest problems so we can direct our work into protecting them and their habitats.
"That's why we are appealing to the public to get involved and look for moths on their patch.
"Without moths, the whole of biodiversity starts to unravel," he added.
The group is asking people to try out bat detectors and moth traps at one of a series of National Moth Night events around the country.
Or, they suggested, "hold your own night-time safari in your garden and report back your discoveries".