UV Light / Moth Sheet

A great way to discover nocturnal Invertebrates is to setup up a ultraviolet light with a white sheet after sunset. While this is typically done to attract Moths, it will also attract many Beetles, Bugs and Flies. In my Backyard Biodiversity project, a majority of the 200+ Moth species I have found have been visitors to this setup.

You’ll need some basic equipment to run your own setup, but it won’t break the bank. The key to a good night of observing is primarily the weather, not your equipment.

To start with you’ll need a light source. Any bright light will attract some Insects. A good place to start is to check out any outdoor lighting you already have to see if it is attracting anything. Try it on a warm, still and humid night. You might find a few species, but unless the lights are exceptionally bright, it’ll be hit and miss.

Setting up a bright light near a white sheet should attract some additional species. The white sheet helps to reflect the light but also makes it easy to spot anything that lands upon it. But if you’re expecting a sheet filled with large colourful Moths, you’ll likely be somewhat disappointed. Typical white lights are not what attracts the Moths.

To ensure a good first impression, you’ll want to start with a ultraviolet light. This really is the only necessary expense. Local hardware stores stock replacement UV globes for bug zappers that are perfect for this application. The higher the wattage, the better. You’ll also need a matching light fitting on extension cord. Then you can mount the light any where suitable. (I use a 50W UV globe and a handheld work light fitting with extension cord).

Pick a suitable night. Thankfully the most appealing evenings for us are also appealing for the Insects. Warm and still nights are most suitable. High humidity helps too. If it’s cold, wet and windy, best to stay indoors.

Hang your white sheet wherever you can. Out in the open works best. Hang from tree branches or between trunks. But hanging at the edge of a patio works almost as well. If there’s a breeze it might be best to secure the lower part of the sheet to stop if flapping around. Secure your UV light in front of the sheet. It can be hung from above or resting on a platform below.

That’s all there is too it. Turn on your light at sunset and monitor it. The first few hours may be quiet. Different species come out at different times of the night. By a few hours after sunset you’ll have a good sampling of species.

The UV light seems dim as it doesn’t put out a lot of visible light. Most of its output is in ultraviolet. This can damage your eyes, so avoid looking directly at the light. Ideally, wear a pair of safety glasses, many of which have good UV protection.

You can collect specimens to take somewhere more suitable to observe or take photos. Or you can observe and photograph them in place on the sheet. For this you’ll need a torch to highlight the specimens. Most cameras will struggle to focus in the dim UV light. Photographing with flash is recommended to freeze any movement.

If you leave the light running long enough into the night, you’ll attract various predator species. On many evenings I have Katydid visitors, and various Spiders and Marbled Geckos come out to feast.

Keep any eye out for Termite alates. Where there is one, there’s usually many more. In a short time you may attract an entire swarm. Not something you want to attract to your backyard. They’ll most likely be present on warm, still nights, especially if it is also humid. If I spot a couple of these, I’ll typically turn the light off and call it a night. Ants have a mid-body constriction (between the thorax and abdomen), whereas Termites do not. Ants have hindwings shorter than forewings, whereas Termites have all four wings equal length.

After taking photographs, upload them to iNaturalist to get assistance with species identification. Many species of Moth are identifiable down to species level with only a photo from above. For other Insects such as Beetles, Bugs and Flies you’ll likely need photographs from a few angles to show diagnostic features.

The more often your run the setup, the more species you’ll find. Some species may only be present for a couple of weeks each year. Run the setup periodically over several years and you’ll start to notice seasonal patterns.

Check out my UV Light / Moth Sheet iNaturalist project where I continue to add new observations from each viewing night. The full list of species observed is shown below, ordered by frequency of observation.

Check out the latest posts on this blog about the UV Light / Moth Sheet backyard incursions.

Unique Taxa Nodes (Minimum Total Species) = 383

Identified to unique Species = 241

Identified to unique Genus = 94

Identified to unique Family = 46

Identifier to unique Order = 2