AAAS: “Many heat-stressed tropical insects are reaching their limits.” It seems intuitive that lowland tropical insects must have evolved to deal with brutal heat. “Compared with mammals, insects are more at the mercy of a hot environment because they can’t cool themselves by sweating or panting.” Their main defense strategies involve avoiding heat by finding shade or burrowing underground. “They can also synthesize ‘heat shock proteins,’ which help prevent other proteins from misfolding or breaking down when exposed to high temperatures.”

Researchers behind the new study tested the responses of 2300 species living in a range of environments + elevations in Peru and Kenya. Ecologist Kim Lea Holzmann…[in] over three field seasons in the Peruvian Andes collected thousands of insects…and put them into small tubes. “Back at camp, she added them to a portable laboratory oven and ramped up the temperature…checked in every few minutes to see which of the various species had stopped moving, which they used as marker of the limit of heat tolerance.” In Peru, flies had the lowest heat tolerance, stopping their movements at an average of 39°C = 102°F. “Beetles could cope with up to 41°C on average, whereas bees and other social insects put up with a bit more.” Grasshoppers and other members of an insect order called Orthoptera were the hardiest: They stopped kicking at 44°C = 111 °F, on average.

“In an analysis that backs up this pattern, Holzmann and colleagues looked at the thermal stability of proteins that are commonly found in major insect groups.” Working from genomic data for 677 insect species, they randomly selected 1000 proteins for each species and had a computer model estimate the temperature at which the protein structure would break down. “The overall pattern mirrored what the team observed in their field experiments: Flies were the most sensitive and orthopterans the most resilient.” In a projection of temperatures by 2100, they estimated up to half of the insects in tropical populations could suffer a ‘heat coma’ after 8 hours of exposure to typical temperatures predicted for the future.

Sobering to say the least. Scary to say the most.