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Question of the month

Sweet basket on a leaf

I noticed a gumleaf was a purple colour, then I found this tiny basket shape on it. It is only about the size of a match head. What is this?

Answer

Basket Lerp (Cardiaspina sp.). Photo courtesy of Steve Wilson.

You have found a lerp. Small bugs called psyllids use their straw-like mouth parts to suck the juices of many plants including eucalypts. Adult psyllids are mobile and can fly but the nymphs are sedentary. These nymphs secrete a sweet solution called honeydew. The sugars and amino acids in this honeydew crystallize and harden in the air, and the nymphs use this substance to build protective covers called lerps. The lerps probably offer the insects some protection from the elements, perhaps creating an enclosed humid enclave.

There are several hundred psyllid species in Australia, and many of these construct distinctive lerps. They range from pale flaky domes to shell-like and conical structures. This one, structured like a fine lacy basket, probably belongs to one of the Lace or Basket Lerps (Cardiaspina species).

Sometimes lerps occur in such numbers that they can seriously affect the health of their host trees. As they feed they remove some of the plant’s chlorophyll causing discolouration. Lace Lerp nymphs turn leaves a mottled red-purple. This discolouration can be seen in the photo. Trees that are already stressed, perhaps by drought or other insect attack, may be more vulnerable to damage.

Not surprisingly, many of these sugary little parcels are prized as food. Indigenous Australians have a long history of harvesting lerps. Some ants actively farm lerps, guarding them from predators in exchange for the sweet rewards. Lerps also provide nourishment for plenty of birds including pardalotes, honeyeaters, bell miners, whistlers, silvereyes and thornbills. Lerps are eaten by mammals such as sugar gliders and possums too. 

Honeydew may even have been mentioned in the Bible. Some scholars believe the ‘manna from
heaven’ that saved the Israelites was in fact honeydew produced by plant-sucking bugs, and
some passages in the Bible imply they ate only manna during their desert sojourn. The Tamarisk Manna Scale (Trabutina mannipara) of the family Pseudococcidae is often considered to be the prime candidate for biblical manna.

Depending on the species, lerps can be sweet, tasty and slightly chewy. They are certainly worth trying provided you know what they are. But don’t be too greedy. Mind your mannas! 

 

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