Light trap
These are traps which use a powerful light source to attract moths and many other insects which fly at night. There are several types available, this one is based on a Robinson Trapwhich generally has the highest capture rates. This one has two actinic flourescent tubes which
emit a blueish light with a high proportion of ultra-violet wavelengths which are particularly attractive to insects. Until they were withdrawn because of the toxicity of mercury, light traps generally used mercury-vapour bulbs which emitted even more ultra-violet light and gave very high capture rates.
.jpg "Photo: By Ben Sale from UK - Near Las Descargues and Gorses - Twin Actinic Midi Robinson, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=63714962")