They look like they’re using bubble gum. Brazilian flies blow out deep brown bubbles of spit every few seconds. Now it seems these bubbles have a serious purpose: to keep the insect cool.

Guilherme Gomes of the University of São Paulo in Brazil and his colleagues placed groups of 50 latrine blowflies ( Chrysomya megacephala ) in transparent cylinders. Then they gradually raised the temperature inside, and took infrared images of the blowflies as they blew bubbles in and out.

As the bubbles went in and out of each fly’s proboscis, both …