The world’s insects are hurtling down the path to extinction, threatening a “catastrophic collapse of nature’s ecosystems”, according to the first global scientific review. More than 40% of insect species are declining and a third are endangered, the analysis found. The rate of extinction is eight times faster than that of mammals, birds and reptiles,suggesting they could vanish within a century. The planet is at the start of a sixth mass extinction in its history, with huge losses already reported in insects.
Butterflies and moths
There has been a “severe reduction” in butterflies and moths in the Kullaberg Nature Reserve in Sweden compared with 50 years ago. Scientists found over a quarter of the 600 species once found had been lost. Butterflies were hardest hit, losing almost a half of species, including the large tortoiseshell and scarce copper. In England, two-thirds of 340 moth species declined from 1968-2003.
Butterflies have declined by at least 84% in the Netherlands over the last 130 years, according to a study, confirming the crisis affecting insect populations in western Europe. A German study found butterfly abundance had declined by 76% over 27 years. Western monarch butterflies, might be gone for good in a few decades. In the 1980s, roughly 4.5 million monarchs wintered in California, but at last count, there may be as few as 30,000. It's a sad reality, a troubling trend that shows a 97% decline in monarch butterflies.
Besides the evaluation if butterfly trends generalise to other insects, the most urgent research needs are understanding the causes of decline and testing mitigation strategies. As butterflies are the best-monitored insect taxa, they are the best indicator of the baseline threat to the 5.5 million insect species, the most diverse group of animals on earth.They are “essential” for the proper functioning of all ecosystems, the researchers say, as food for other creatures, pollinators and recyclers of nutrients. “The butterfly trends confirm that the sixth major extinction event is profoundly impacting the life forms of our planet. This decline in global butterfly population is due to use of pesticides, intensification of agriculture, climate change and loss of habitat.
A butterfly has four wings – two on each side. They are broken into two forewings and two hindwings. When a butterfly is in flight, the wings move up and down in a figure-eight pattern. Butterfly wings are made up of two chitonous layers (membranes)and are transparent in colour. Each wing is covered by thousands upon thousands of colourful scales and hairs. Most butterflies have different patterns on the front and back of their wings.
When light hits the different layers of the butterfly wing, it is reflected numerous times, and the combination of all these reflections causes the very intense colours that you see in many species.
The diversity in the appearance of the dorsal and ventral wings of many butterflies has evolved depending on what the wing surfaces need to do, researchers say. When the butterflies are resting with their wings closed, the ventral surfaces are exposed; the patterns on these surfaces usually enable camouflage and avoidance of predators. On the other hand, dorsal surfaces, visible when the wings are open, often have colours and patterns that specifically attract potential mates.
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