Bycatch

Identifying the intruders in your moth traps

February 2026

 The bycatch attracted to moth lights can be a mixed blessing. On the one hand, a clatter of May Bugs in early summer followed by swarms of Wasps and scary Hornets later in the year are a bit of a nuisance. On the other hand, accidental captures can open up a whole new field of study for the curious naturalist. More than 40,000 invertebrates are recorded in the UK, including over 24,000 insect species, putting the 2,500 or so UK species of Lepidoptera into perspective. Occasional vertebrates are also found in moth traps, with bats, birds and mice not unknown.

Identifying your visitors

As many of you will know, a wide variety of species, not all nocturnal, can appear in traps alongside the moths. So, where do you start with putting names to some of these creatures? As with moths, it's best to familiarise yourself with the most common and easily identifiable species: new species will then stand out from the crowd. We're fortunate to live in an age when more identification aids are available than in the past. Some you may find useful are:

• ObsIdentify: a free phone app founded in the Netherlands that attempts to identify a species from an uploaded photograph. It relies on good-quality images that show the necessary identification features and, although not always accurate, it can guide your research; it can also be useful for moth identification.
• iNaturalist: an American app, but also global, through which sightings can be shared and help obtained.
• NatureSpot: a more local website covering wildlife in Leicestershire and Rutland. It's easy to navigate, with photographs of many species likely to be seen in our region.
• iSpot: an online community for wildlife sightings in the UK and Ireland (I haven't tried this one yet).

There are also plenty of websites and books that specialise in specific groups of wildlife.

Connecting with other bycatch enthusiasts

A Facebook group called Moth Trap Intruders UK has been running since 2017 and regularly posts a compilation of the ten species most likely to be seen in any given month (based on records received). It also hosts a useful files collection on specific groups. Photographs can be posted on the site for identification guidance from many specialists, some of them national experts.

I was surprised to see that I had made 125 posts to this group since it started, reminding me of past encounters with many species from Springtails to Great Diving Beetles. It's a useful way of looking back on sightings, both mine and other people’s. My bycatch has included:

• Mice, a bat and a frog (vertebrates)
• Butterflies, dragonflies and spiders (occasionally)
• Flies in all their forms, ground and water beetles, and parasitic wasps (mainly)

I've heard of people having birds in their traps, including someone who once found a Puffin in their Skinner trap on a remote headland. I post many of my finds, along with a photograph for identification verification, to iRecord; this in turn adds to the National Biodiversity Network Atlas, and both are useful resources.

Anonia purmunda (fly)

 

Anthocomus fasciatus (beetle)

 

Yellow Mayfly

 

Wasp Spider

 

Yellow Scorpion

 

Painted Lady