The key to the climatic survival of butterflies may be color-coded

Butterflies fly over some plants at Hankou Park in Wuhan, central China’s Hubei province, on May 16, 2020 (Photo by Hector RETAMAL / AFP)

PARIS – A butterfly’s ability to absorb or reflect the sun’s heat with its wings could be a matter of life and death in a warming world, according to British research published Thursday calling for gardens, parks and farms to house shade and cooling. places.

While all butterflies are ectotherms (they cannot generate their own body heat), the ability to regulate temperature varies significantly, the researchers said.

The study found that species struggling to moderate their body temperature often depend on being able to escape the full heat of the sun in shady “microclimates” to survive.

These butterflies “are likely to suffer the most from climate change and habitat loss,” said lead author Andrew Bladon of the Department of Zoology at the University of Cambridge.

The researchers said the cooler niches they depend on have shrunk as habitat is lost and fragmented, driving population declines in two-thirds of the butterfly species in Britain.

This is exacerbated by extreme weather events and temperature fluctuations made worse by climate change, they said.

To measure how different butterflies cope with temperature change, the researchers captured 4,000 wild specimens of 29 species, combing various UK sites in monthly surveys from April to September 2009 and May to September 2018.

They recorded the behavior of each butterfly and then, if they could catch it in their nets, they took its temperature with a tiny 0.25-millimeter-thick thermometer.

The study found that larger, pale-colored butterflies, such as the Large White or Brimstone species, are better at thermoregulation because they can tilt their wings to reflect the sun’s heat away from them or onto their bodies to reach the proper temperature.

Population decline

The researchers said these species had stable or growing populations.

But among species with smaller or more colorful wings, they found a less rosy image, particularly among “thermal specialists” who use shade to cool off.

These species, such as the Small Copper butterfly, have suffered steeper population declines in the past 40 years, according to the study, which was published in the Journal of Animal Ecology.

Bladon said that landscapes must become more diverse to protect a variety of butterfly species.

“Even within a garden lawn, patches of grass can be allowed to grow longer; these areas will provide cooler, shady places for many species of butterflies, ”he said in a university news release.

“We also need to protect features that break the monotony of agricultural landscapes, such as hedges, ditches and patches of forest.”

Insects, including butterflies, are the world’s top pollinators: 75 percent of the world’s major food crops depend on animal pollination, according to the UN.

Fear of food

In another study also published Thursday, researchers from the University of Michigan found that projected temperature increases can cause alterations in the shape of the wings of North American monarch butterflies and could impede their annual migration.

The researchers raised Monarch larvae at 25 degrees Celsius or a high 28C by feeding them three species of milkweed: common, swampy and tropical.

Each of these contains cardenolides, a steroid stored by monarch larvae as a chemical defense against predators and an antibiotic against parasites that can be toxic in higher concentrations, the researchers said.

Cardenolide levels are particularly high in tropical milkweed, which has proliferated due to increased temperatures.

The researchers found that larvae reared in warmer temperatures flew for shorter periods and at a reduced distance, while expending more energy per measured distance.

The study, published in the Journal of Insect Conservation, also found that those who had been fed cardenolide-rich tropical milkweed had shorter and wider front wings.

The researchers said that these rounder wings were less efficient for long-haul flights than the long, narrow wings that can be used for power-saving gliding, concluding that this could hamper annual migration.

Most Monarch butterflies in North America travel several thousand miles to winter in Mexico, where they mate.

The study said that monarch populations had seen a “drastic” decline in recent decades, with those that migrated eastward fell by around 80 percent, while those that migrated westward dropped by 99 percent. since the 1980s.

/ MUF

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