A plant stem and leaf covered in foam that contains a small insect

A baby froghopper, or nymph, sits inside the bubbly foam protection it has made for itself © RECEP_OZTURK/ Shutterstock

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Cuckoo spit and fascinating froghoppers (spittlebugs)

In spring and summer, you might notice white foam on plants that looks like frothy spit on a plant. Reassuringly, it's not spit at all, but foam made by a harmless insect called a froghopper - also known as  a spittlebug.  If you look closely, you will see a delicate, green baby froghopper nestled within the white foam. 

Froghoppers are bugs that are found all over the world and are related to cicadas. They hold their wings in a roof shape over their body and have a mouth that can pierce plant stems and suck the sap contained within. 

What is cuckoo spit and where does it come from?

Cuckoo spit - so named because it appears in spring when the cuckoo first calls - acts as protection, or bubble wrap, for the baby froghopper.

Also known as a nymph, the baby froghopper taps into the sap of the plant, then eats and exudes it, frothing and bubbling it around itself. The slippery foam stops it from dehydrating and hides the nymph from predators such as ants. The foam also protects the nymph from parasitic wasps, who find hard to stand on the foam's surface as they try to lay their eggs inside the baby froghopper's body. 

The nymph makes the foam by extruding the plant sap out of its anus and frothing it - a little like a cappuccino maker.  

A small insect nymph crawls along a plant stem and behind it is a frothing foam

Nature's cappuccino maker, a froghopper nymph in its foam © Sandra Standbridge/ Shutterstock

What species of froghoppers are you likely to see in the UK?

You might see two main species of froghopper in the UK: the common, or meadow, froghopper (Philaenus spumarius) and the black-and-red froghopper (Cercopis vulnerata) with its distinct markings.

Museum beetle curator Max Barclay says that if you have seen cuckoo spit in your garden or park, it has most likely been made by the nymph of the common froghopper. These froghoppers like to move into new areas and are found across the UK in good population numbers. If a lawn or grass is left to go wild, the common froghopper will quickly move in.  

Adult common froghoppers are about half a centimetre long. To reach new areas, they can fly high in the sky and be carried by the wind, though this makes them prone to getting eaten by swifts and swallows as they make their journey. 

The Latin name for the black-and-red froghopper, Cercopis vulnerata, means wounded and refers to the red markings on its body. This species makes a bigger foam bubble than the common froghopper and the adults grow to be around a centimetre long. You'll only see this froghopper in meadows and woodland outside of a town or city, as it prefers an undisturbed habitat. Numbers of the black-and-red froghopper have declined in recent years, probably due to the clearing of hedgerows and insecticide drift.

In total, there are 10 species of froghoppers in the UK. 

An adult common froghopper

An adult common froghopper can jump up to 70 centimetres into the air to escape a predator © Eduardo Dzophoto/ Shutterstock

What do froghoppers (spittlebugs) look like? 

Froghoppers have large eyes and very good vision. They can also jump up to 70 centimetres high into the air to evade predators. 

They have a beak at the front of the head that is used for drilling into the plant to find sap to feed on.

A lot of froghoppers produce sound to communicate with each other. When they are comfortable and happily sucking on the sap of a plant, froghoppers might start to chat to each other, although the sounds they make are out of the range of what we can hear. 

An adult froghopper might live for up to three months. They are fairly robust and durable and can mate several times throughout the summer.

In winter, the adult froghopper will lay around 100-200 eggs on a plant, which then hatch in the spring. After emerging from the egg, the baby froghopper produces and stays inside its bubble of cuckoo spit for a couple of weeks. Once it has grown to full size, its back splits open and it emerges from this casing in adult form with wings and wing cases that protect it from predators.   

Froghoppers are from the order Hemiptera, or true bugs. There are three suborders of true bugs, and froghoppers are in the suborder Auchenorrhyncha, which are sap suckers that include cicadas. The other two suborders are Heteroptera, which include shield bugs, bed bugs and assassin bugs, and Sternorrhyncha, which are small, soft-bodied bugs that include many plant pests such as aphids, greenfly and scale insects.

A red and black bug on a green plant

The black-and-red adult froghopper can grow to be almost a centimetre long. This froghopper prefers to live in undisturbed woodland margins. © Lukas Zdrazil/ Shutterstock

What's the deal with parasitic wasps and froghoppers?

If you see a froghopper nymph with a lump, or gall, on its side it is probably the egg of a parasitic wasp. The parasitic wasp lays its eggs inside the froghopper nymph so that when the baby wasp hatches, it can eat its way out from the inside of the froghopper.

To defend itself from such a horrible fate, the froghopper uses cuckoo spit as protection. The wasp can't stand on the shifting surface of the foaming mass of cuckoo spit and so can't get a good enough grip to lay its eggs in the nymph's body.  

A plant and froghopper nymph

Two nymph froghoppers shelter in cuckoo spit © Tomasz Klejdysz/ Shutterstock

Is cuckoo spit harmful to humans and do spittlebugs bite?

Froghoppers, or spittlebugs, are completely harmless to humans. While we probably wouldn't encourage it as part of your regular diet, Max Barclay from the Museum says you could probably even eat them, although the black-and-red froghopper would probably taste a little bitter. 

Do froghoppers damage plants?

If there are enough of them, froghoppers might damage the plant, as they are sucking its sap, but in smaller numbers, the plant can afford to feed a few resident sap-sucking froghoppers.

In the winter months most of the froghoppers hibernate. 

Outside of the UK, froghoppers are innocent carriers of a bacteria called Xylella fastidiosa, which causes a number of diseases in plants. This bacteria can be carried by froghoppers as they fly from plant to plant, piercing their stems in search of sap. In areas that do not yet have Xylella fastidiosa, such as the UK, froghoppers pose no threat as carriers. 

How to get rid of cuckoo spit from a plant

Cuckoo spit is harmless and won't hurt the plant. The nymphs that make the cuckoo spit will naturally turn into adults and fly away to find new pastures. 

Froghoppers are an important part of garden and park biodiversity. They are also an important food source for swifts and other birds. 

It's best to leave froghoppers alone as they complete their life cycle and turn from a nymph to adult in the spring. If you really want to remove cockoo spit, it can be hosed or wiped off the plant.