How do spittlebugs breathe through foam?
The protective cuckoo-spit nests whipped up by sap-sucking froghopper nymphs present an obvious problem to an air-breathing insect – it’s very wet in there. Even if they don’t drown, you’d think the accumulation of exhaled CO2 would be fatal. It was only recently discovered that the nymphs use their telescopic abdomens as snorkels, pushing the tip out of the nest to fill their spiracles (respiratory openings) with fresh air. This is not possible, though, during their final moult, when their abdomens lose their elasticity. Instead, they burst many of the tiny bubbles within the nest to create an air-filled chamber, which sees them through until their adult cuticle has hardened and they can leave the nest.
Excrete liquid via the anus, pump it full of air and voilà – a shield of bubbly foam.