Where Have All The Insects Gone?
As with many posts, this one began its formation at the nature reserve. A warm day of sunshine and blue skies, camera ready, and I set off. Some years ago I had the best summer ever at the reserve, in terms of sightings. Not just birds and mammals, but insects almost everywhere I looked. This year, as I walked, the scarcity of the latter was notable. Where have all the insects gone?
Declining Numbers
A couple of days after my visit, I received the latest Buglife newsletter. This included a feature on the most recent Bugs Matter Citizen Science Survey, which demonstrates continuing decline in Britain’s insect numbers. Findings showed a 78% drop in the number of winged bugs hitting car vehicle number plates between 2004 and 2023. This simple measure, also known as the Windshield Effect, is a powerful indicator of disappearing insects.
We know insects are important. Their free services include pollination, decomposition of rotting plant matter, and sustenance for other pollinators (such as bats). Their numbers are being impacted by humans through habitat destruction, pollution, pesticides, and climate change. I’ve left the garden wild again this summer, but the buddleia is noticeably absent of the usual humming of bees and colour of butterflies. Though insects might be towards the bottom of the food pyramid, if the base is removed, the impact is felt at every level up to and including the top.
Butterflies and Moths
Years ago, summer walks included nature discovery. Caterpillars were a particular feature – usually small tortoiseshell (stinging nettles, July) and peacock (stinging nettles, June/July), but also cinnabar moth (ragwort, July/August) and various hawk moths (usually have a ‘horn’ at the end of the tail). Today such regular sightings are much rarer. Myriad factors influence the decline in butterfly and moth numbers, including the destruction of food plants, and pesticide use.
Ragwort but no cinnabar moth caterpillars. A 2003 study showed that although the distribution of cinnabar moths remained steady, their numbers declined dramatically between 1968 and 2002. This is largely due to the destruction of their main food source, ragwort, which is toxic to livestock.
Small tortoiseshells are thought to have been impacted by the arrival of the Sturmia bella fly from Southern Europe. First recorded in Britain in 1999, the fly has benefitted from climate change. It lays its eggs on the stinging nettle, which are then consumed by the small tortoiseshell caterpillar. The fly larva hatch and eat the caterpillar from the inside out.
Butterflies are ectotherms. That is, they rely on the external environment for their body heat (as opposed to endotherms which generate their own body heat). As ectotherms, butterflies are very responsive to climate changes. Half of Britain’s butterfly species are threatened, or near threatened, with extinction. The Big Butterfly Count 2024 runs between 12 July and 4 August, and hopes to help understand how butterflies (and daytime moths) are responding to the changing climate.
Common Themes
Insect decline is a global issue. Over the last 50 years, the worldwide insect population has declined by 75%. Insects are responsible for the pollination of 80% of trees and plants on the planet. It is a complex relationship of coexistence, and evolution.
Some plants have evolved so that only one type of insect can pollinate them. The Madagascan star orchid, for example, can only be pollinated by Wallace’s sphinx moth (also known informally as ‘Darwin’s moth’). The flower and moth are uniquely adapted to each other. One with a 30 cm long nectar tube, the other with a 28 cm long proboscis.
Global issues need global action. In this case to protect and restore natural habitats, reduce pesticide use and combat climate change. Public awareness and education are also needed in order to develop deeper understanding of the importance of insects and what we can do to support them.
We’re leaving the old world behind through our impact on the planet … the simple summer holiday walks of the 70s and 80s where we spotted caterpillars are experiences I fear today’s children will never have. This year’s buddleia is just a buddleia. No longer a butterfly bush.
We must act now to protect insects. It’s no exaggeration to say that our future depends on it.
The State of Nature Report 2023 found that since 1970, pollinating insects such as bees, hoverflies and moths, have decreased by an average of 18% across the UK. Meanwhile, predatory insects, such as ladybirds which help control crop pests, have declined by more than a third (34%).
‘If we and the rest of the back-boned animals were to disappear overnight, the rest of the
world would get on pretty well. But if the invertebrates were to disappear, the
world’s ecosystems would collapse.’ Sir David Attenborough
Thanks for that very interesting piece Emma. I have alot of flowers in my garden but haven’t heard the humming of insects nor seen butterflies
Sad and scary for the future.
Thank you for reading, and commenting, Eileen. I was at the reserve again yesterday, and although there were a number of dragonflies, people agreed that there are far fewer than usual. I think that schools are raising awareness of ecology and the environment, alongside initiatives such as Roots and Shoots. It’s too late to change some things, but hopefully today’s children will be more conscious of the need to nurture and protect the planet than previous generations have been.