How do spit­tle­bugs breathe through foam?

BBC Wildlife Magazine - - Our Wild World - SB

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.

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