Wayne Smith posted this photo to the Australian Pest Managers Network, with the following -
“They are about 10 mm long. House backs on to a cane field and cane is fully grown about to be harvested. They are living in the shrubs around the house and cover the walls when disturbed.”
I managed to ID them, but would have failed if it wasn’t for the mention of Sugar Cane.
The genus Phaenacantha includes a number of pests of sugar cane, which explains why some of the species have binomials like saccharicida, and the Australian species was recognised as a potential pest of Sugar Cane as far back as 1921. They weren’t wrong, either - the population of Linear Bugs can explode to devastating proportions, not least because they’re vectors of plant disease, on top of all the damage they do to the plant as they feed on the sap.
There are a few predators of them, luckily - ants will eat the eggs after they’ve been scattered around the base of the plant, and maul the nymphs and adults, and assassin bugs will gorge themselves, but in a large field of sugarcane one of the few things that will reduce the number of the pests is to burn the whole thing to the ground, after the best parts of the cane have been harvested.
The family, Colobathristidae, used to be part of the Lygaeidae, but got split off into their own group in 1997.
Galls formed by Armoured Scale Insects, on a Flooded Gum (Eucalyptus rudis).
Gall formation is not usual for the Armoured Scale Insects - most of the 2650 described species from the 400-odd genera produce a waxy protective scale while they feed on the host plant. Diaspidid scales are usually more complex, waterproof, and substantial than those of most other families, incorporating the molted skin of the first two instars, and sometimes frass and fragments of the host plant.
Some Diaspididae are serious agricultural pests - one, Quadraspidiotus perniciosus or San Jose scale, was the first known example of insecticide resistance, in 1914.
From the Dryandra Woodlands.
Identified as Apiomorpha helmsii on Bowerbird by Lyn Cook, an expert of Apiomorpha galls. The female galls are much larger, and spindle-shaped, but are also strongly fluted.