August 2013

Mysterious foam

I was wondering if you could help me to identify some strange foam found near a creek on our property.

Answer

Spittle bug foam on a tree branch Foam of Spittle bug

The foam has been made by Spittle Bugs (Amarusa australis). These sap-sucking insects hide underneath the foam, that they make themselves. The foam is made by bubbling air through the excess fluid ejected from their posterior. You will probably find that the ground underneath will be wet and will eventually darken with Sooty Moulds that grow on the undigested sugars in the foam. If you wipe the foam from a piece of branch you should be able to see the insects.

Spittle bugs belong to the same Order as other True Bugs, such as Cicadas and Stink Bugs. The True Bugs (Order Hemiptera) are different from many other types of insects in that they all possess piercing and sucking mouthparts. While most – like Spittle Bugs and Cicadas – use their straw-like mouthparts to suck sap from trees, others (like Assassin Bugs) are predators and use them to kill and suck dry other insects.

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