Nocturnal Moths Are More Efficient Pollinators Than Bees

A new study by researchers at the University of Sussex suggests that moths are more efficient at pollinating during the night than day-flying pollinators such as bees. The research is published in PLOS One.

Don’t forget about moths

Populations of wild pollinator insects are declining globally due to the fragmentation of habitats, pesticide use, the effects of climate change, diseases, parasites and predators. Now, Dr. Fiona Matthews, professor of environmental biology, and colleagues demonstrated that moths have a high pollination efficiency, making them important players in the health of our ecosystems.

The researchers studied the contribution of both nocturnal and non-nocturnal insects – like moths – to the pollination of bramble across 10 sites in the South East of England throughout July 2021. “Moths are a highly diverse group of invertebrates that are considered to be the main contributors to nocturnal pollination. Despite moths comprising 88–91% of all described Lepidoptera, they are subject to a disproportionately low level of research compared with butterflies,” the researchers write.

Matthews and colleagues used camera traps to study flower visitation and pollen deposition of each site for a period of three days and nights. “The number of bramble flower-visiting invertebrates was determined by taking interval photographs of flowers during the day and night. Six wildlife cameras (16-megapixel) with infrared low glow technology, were set to take photographs every 30 seconds over a period of three days and three nights at each site,” the scientists explain. To preserve battery life, the cameras were deactivated between 4pm–7:10pm during the study.

To analyze pollen deposition, the researchers grouped buds of bramble into treatment groups:

• Diurnal – where muslin bags were removed at sunrise and replaced at sunset in order to expose the flowers during the day only
• Nocturnal – where muslin bags were removed and replaced to ensure that the flowers were exposed from sunrise until sunset
• Unvisited control – where flowers were bagged throughout the sampling period to prevent visitation from any pollinating insects.

The buds of bramble were collected after the sampling period, and the total number of pollen grains was determined for each stigma. Pollen rate – the hourly rate of pollen grain deposition – was determined by dividing the total pollen by the amount of time each treatment group was exposed to pollinating insects.

Moths are efficient pollinators

The Sussex team discovered that 83% of insect visits to bramble flowers were made during the day. Moths made fewer visits during the shorter summer nights – accounting for 15% of the visits – but they were able to pollinate the flowers more quickly.

“Moths are important pollinators, and they are greatly under-appreciated and under-studied. The majority of pollination research tends to focus on day-flying insects, with little understanding of what happens at night,” says Dr. Max Anderson, co-author of the study and now a South West Landscape Officer at the Butterfly Conservation.

“Now we know that moths are also important pollinators, we need to take action to support them by encouraging some bramble and other flowering scrub plants to grow in our parks, gardens, road verges and hedgerows.”

It’s important to note that the short duration of the study and the locations used may limit how representative the results are of the wider bramble and insect populations across other locations.

However, the researchers emphasize that their data showcases that bramble, which is often cleared away and considered unsightly, is a valuable foraging resource for both day-time and night-time pollinators. “Our work shows that simple steps, such as allowing patches of bramble to flower, can provide important food sources for moths, and we will be rewarded with a crop of blackberries. Everyone’s a winner!” Matthews concludes.

Reference: Anderson M, Rotheray EL, Mathews F. Marvellous moths! pollen deposition rate of bramble (Rubus futicosus L. agg.) is greater at night than day. PLOS ONE. 2023;18(3):e0281810. doi:10.1371/journal.pone.0281810

This article is a rework of a press release issued by the University of Sussex. Material has been edited for length and content.