Migratory hoverflies provide key ecosystem services
Posted in:
Biodiversity, Ecological Indicators, Ecosystem Services, Hoverflies, Invertebrates
Date posted: 8 July 2019
By Edward Lim 08.07.19
UK hoverflies as pest predators
Each year an inordinate number of insects take to the skies to migrate large distances across countries and continents. Some species have received more attention than others, often due to the immediate and devastating impact they can have on human societies, e.g. locusts. Other migratory species, such as many of the 250 species of hoverfly found in the UK, actually provide important ecosystem services; hoverflies are key pollinators of crops and the larvae are predators of aphids, one of the UK’s most abundant crop pests. However, until recently little work had been done to quantify the beneficial impact that migratory hoverflies have.
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Inward migration
A new study by Wotton et al. (2019), published in Current Biology, in which hoverfly migration was analysed using ten years of data from vertical-looking entomological radars, found that a staggering total of between 1 and 4 billion hoverflies migrate between Europe and southern Britain each year. They calculate that this results in the consumption of an average of 6 trillion aphids in southern Britain by the larvae (i.e. offspring) of migrant hoverflies each year, which amounts to one-fifth of all pest aphids in an average arable field. Furthermore, a key finding of their study was that, unlike the serious population declines characteristic of many of the UK’s insect pollinator species, the study found no downward trend in the population of migrant hoverflies over the 10 year period.
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Other ecological benefits
The influx of hoverflies into Britain each year is also of great ecological importance. Hoverflies are important pollinators of wildflowers, and as a migratory species Wotton et al. (2019) suggest that they contribute to maintaining high genetic diversity within wildflower populations through the transfer of pollen across long distances. In order to investigate this, the researchers analysed pollen samples from Episyphus balteatus and Eupodes corolla, two migratory hoverfly species, and calculated that between 3 and 8 billion grains of pollen are transported to southern Britain by these two species each year.
Reference: Wotton et al., Mass Seasonal Migrations of Hoverflies Provide Extensive Pollination and Crop Protection Services, Current Biology (2019). https://doi.org/10.1016/j.cub.2019.05.036
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