Moth Trapping - Monitoring Nocturnal Pollinators
Enhancing green spaces in London where all natural pollinators can thrive, and their habitats can be enjoyed by all.
Moth Trapping - Monitoring Nocturnal Pollinators
Why Moths Matter
It is a common misconception that all moths eat clothes. In reality, only a small number of UK moth species – predominantly clothes moth species such as the common clothes moth (Tineola bisselliella) – consume textiles, and only in the larval stage. Many moth species do not feed at all as adults, and most play important ecological roles.
Moths are increasingly recognised as valuable pollinators. While bees are well studied, moth pollination remains less thoroughly understood, largely because most moth activity occurs at night. Research published in recent years has found that moths visit a surprisingly wide range of flowering plants, sometimes including species also visited by bees during the day. Plants particularly associated with moth pollination include night-scented stock, white campion, red campion, evening primrose and honeysuckle – species that are often pale-coloured, strongly scented after dark, and shaped to accommodate moth feeding.
Monitoring moth populations helps us better understand biodiversity and ecosystem health, and provides data that cannot be obtained from daytime surveys alone.
What Is Moth Trapping?
Moth trapping is a widely used ecological monitoring method involving the use of light to attract moths, temporarily capturing, identifying and recording the species present, then releasing them unharmed. This method provides important data on species diversity, population trends, habitat quality and environmental change. Long-term moth records help identify the impacts of climate change, habitat loss and pesticide use.
How Moth Traps Work
Moths are attracted to artificial light, particularly ultraviolet (UV) wavelengths. The reason for this attraction has been the subject of scientific debate for many years. The traditional explanation – that moths use the moon as a navigational reference point and mistake artificial lights for the moon – has been increasingly questioned. More recent research (including work published in Nature Communications, 2024) suggests that moths navigate by maintaining a constant angle relative to a light source, a behaviour that works well with the distant sun or moon but causes them to orbit close artificial lights. For the purposes of running a moth trap, the mechanism matters less than the practical result: moths reliably come to light, particularly UV light.
Modern moth traps typically use actinic fluorescent tubes or UV LED bulbs. Traditional mercury vapour bulbs – long considered the gold standard for attracting numbers – are increasingly difficult to obtain and less commonly used in new equipment. A typical trap includes a UV bulb, a funnel or entrance through which moths descend, a collection chamber, and egg cartons or similar structures inside for moths to rest on. Moths enter overnight and settle safely inside, where they can be identified and recorded the following morning before release.
Running a Moth Trap: Practical Guidance
Choosing a Trap
Different trap types vary in brightness, cost and portability.
- Brighter traps (such as those using actinic tubes or mercury vapour bulbs) attract more moths but consume more power and may disturb neighbours in residential settings.
- Smaller LED-based traps are more portable, energy-efficient and less costly, and are a practical starting point for beginners, though they may attract lower numbers.
Choose a trap appropriate for your setting and purpose.
Placement
- Position the trap away from competing artificial light sources
- Avoid placing it directly under bright street lighting
- Use in open areas where moths can approach from multiple directions
- Follow all safety precautions provided with your equipment when handling electrical components outdoors
Weather Considerations
Moth activity is significantly influenced by weather conditions. The best nights for trapping are:
- Warm – temperatures above approximately 10°C
- Calm – low wind speeds
- Overcast – cloud cover helps retain warmth and reduces competing moonlight
Cold or windy nights typically produce very low numbers. The warmest months (June to August) generally produce the highest diversity, but early season trapping (April to May) can reveal important species not present later in the year.
Recording and Identification
When checking your trap:
- Handle insects gently – hold specimens only if necessary for identification, and use a clear plastic pot if you need to examine a moth closely
- Photograph specimens before releasing them, particularly any that are unfamiliar
- Use reliable printed or digital identification guides – the Field Guide to the Moths of Great Britain and Ireland (Waring, Townsend & Lewington) is the standard reference
- Record your findings systematically, noting species, numbers, date, location and weather conditions
Records can be uploaded to iRecord or submitted to your local moth recording group. Online identification communities (such as the Upper Thames Moths Facebook group or similar regional groups) can assist beginners with unfamiliar species.
Why Moth Monitoring Matters
Moths form a significant part of the food web, supporting bats, birds, small mammals and other invertebrates at multiple life stages – both as caterpillars and as adults. Monitoring helps detect biodiversity changes, assess habitat management outcomes, inform conservation strategies and track long-term population trends. Including nocturnal species in surveys provides a far more complete picture of urban biodiversity than daytime monitoring alone.
Key Takeaways
- The vast majority of UK moths do not eat clothes – only a handful of species do so, and only as larvae
- Many moths are valuable pollinators of night-flowering plants
- Light trapping is a safe and well-established monitoring method
- Long-term trapping data reveals ecological trends invisible to other surveys
- Nocturnal monitoring complements daytime surveys and completes the picture of urban biodiversity