Scientists warn: collapse of iconic insect species threatens our future

Scientists in Costa Rica are warning of the consequences of a steep decline in the population of a previously common insect.

“Alarming” decline

As reported by the Tico Times, an English-language newspaper in Costa Rica, May beetles - referred to in Spanish as “abejones de mayo” - are disappearing in the Central American country “at an alarming rate”.

Generally most active around this time of year, the insects are well known in Costa Rica as a signal of the onset of the rainy season.

But the Tico Times cites biologists at the University of Costa Rica (UCR) as estimating that the May beetle’s population has declined nationwide by 90 to 95% over the past 40 years.

Why is this happening?

This negative trend, UCR’s Ricardo Murillo tells the media outlet, appears to have been caused by three chief factors: urbanization, pesticide use, and climate change.

Urban expansion in Costa Rica has reduced the number of natural spaces in which May beetle larvae can develop, and the deployment of pesticides in the agricultural industry has a harmful physical impact on the insects. Pesticides have a debilitating effect on May beetles and hamper their ability to reproduce.

Climate change, meanwhile, has disrupted the “seasonal cues” that influence the beetles’ reproduction, the Tico Times says.

Why do we need May beetles?

Speaking to the Spanish newspaper El País, Murillo’s UCR colleague Andrés Arias notes that May beetles may be a significant pest to Costa Rica’s farmers, but they also make a major contribution to the local ecosystem.

“They’re a serious problem for the agricultural community,” Arias told El País, explaining that the beetles’ larvae damage crops by feeding on their roots. “This affects the production of things like potatoes, coffee and sugar.”

However, Arias pointed out that the “other side of the coin” is the role May beetles play as pollinators - carriers of pollen from the male part of a flower to the female part of the same or another flower.

As is outlined by the U.S. Department of Agriculture (USDA), pollination is a crucial process within Earth’s ecosystem.

“The successful transfer of pollen in and between flowers of the same plant species leads to fertilization, successful seed development, and fruit production," the USDA says.

The body adds: “Of the 1,400 crop plants grown around the world, i.e., those that produce all of our food and plant-based industrial products, almost 80% require pollination by animals.”

Arias also highlights that May beetles are a key source of food to certain birds and mammals, and contribute to increasing the fertility of soil.

“They feed on organic matter, breaking it down so it can be more easily absorbed by the soil,” he told El País. “What’s more, their movements create spaces in the earth that allow for greater circulation of air and water.”

Vanishing insects a major global issue

The rapid drop-off in the population of Costa Rica’s May beetles comes against the backdrop of a major decline in overall insect numbers worldwide, caused by human-made changes to the planet.

Described by the University of Connecticut’s David Wagner as “the fabric tethering together every freshwater and terrestrial ecosystem across the planet”, insects are suffering a 2% global reduction in population each year, according to a 2022 report by Reuters.

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