Lerp Psyllids: these insects feed on plant sap and then use the expelled sugar to build protective structures around themselves
Above: three different species of lerp psyllid
These tiny, aphid-like creatures are commonly known as lerp psyllids or jumping plant lice. Their nymphs have specialized mouthparts that can extract the sap from certain plants, and the sugar is then excreted as a liquid that quickly crystalizes when it hits the air, allowing the nymphs to build intricate structures known as lerps.
Above: psyllid nymphs hiding beneath their lerps, likely Creiis corniculatus and Creiis costatus
As this article explains:
Lerps are basically pure starch with some proteins and fats. They are created by psyllids, which are tiny, sap-sucking insects. When psyllid nymphs imbibe tree sap, their gut absorbs the amino acids and nutrients, but they quickly excrete the water as honeydew and the sugar as lerps.
Above: the lerps of two different psyllids from genus Cardiaspina
Each species produces its own distinctive type of lerp. Some of these structures resemble clamshells, while others have a fuzzy, glassy, or basket-like appearance; most lerps measure roughly 1-5mm in diameter, but some have a wavy or tube-like shape that can extend to a length of more than 10mm.
Above: a pair of exposed psyllid nymphs
These structures provide the nymphs with some measure of protection from parasites, predators, and dehydration, but they can also attract some unwanted attention:
Unfortunately for psyllids, their homes taste sweet (containing more starch than cane sugar) and are a prized food of birds, mammals and opportunistic humans. The level of sweetness fluctuates depending on the season, the weather, and the species of psyllid.
Above: animals feeding on some sweet, delicious lerps
The nymphs themselves are tiny, and their bodies often have a flat, oblong shape that allows them to slide beneath their lerps more effectively. They spend all five stages of their nymphal development tucked beneath their lerps; if the structure is damaged, removed, or destroyed, the nymph immediately begins to construct a new one.
Above: genus Hyalinaspis and genus Cardiaspina
When the nymph finally reaches maturity, it sheds its exuvia (molted exoskeleton) and emerges from the lerp as an adult psyllid. The adults are winged insects that look like miniature cicadas, with their bodies typically measuring less than 5mm long (that's about 1/5th of an inch).
Most lerp-forming psyllids are native to Australia, but they also occur as an invasive species in many other parts of the world.
Above: nymphs of genus Glycaspis and Cardiaspina
Lerps have traditionally been incorporated into the beliefs and practices of Aboriginal cultures in Australia, which is home to more than 300 different species of lerp-producing psyllid:
Lerps feature in Aboriginal calendars, ceremonies, mythology, and cosmology, all of which have embedded biocultural knowledge about the time and place for optimal collection. These insects are central to Indigenous cultures, yet Western science knows surprisingly little about their taxonomy, biology, and ecology.
The term "lerp" actually comes from the indigenous word lerep, which means "sweet" in the Wemba-Wemba language of southeastern Australia.
Above: Eucalyptolyma maideni, also known as a spotted gum lerp psyllid, hiding beneath its fern-like lerp
Sources & More Info:
Land for Wildlife: Lerps: One of Nature's Sweet Offerings
Business Queensland: Psyllids and Lerps
Journal of Ethnobiology: Indigenous Use of Lerps in Australia: So Much More than a Sweet Treat
Aboriginal Peoples and Terrestrial Invertebrates in Australia: Lerp and Honeydew
iNaturalist: Subfamily Spondyliaspidinae
Brisbane Insects: Lerp Insects