By Emma Rooksby, coordinator of Growing Illawarra Natives
Social media is lighting up in 2025 with images of all kinds of insect: native bees, bugs, beetles, flies, wasps and many more. Invertebrate biodiversity really seems to be having a moment. I normally use this column to write about plants, but am switching things up a bit this week to cover some of these critters that interact with Illawarra's local native plants, namely stink bugs! (And I promise, there's a direct link with the article about Swamp Hibiscus I posted last week.)
Pretty well everyone who has a citrus tree in a pot or in the garden is familiar with the Bronze Orange Bug (Musgraveia sulciventris). This sap-sucking bug is native to coastal eastern Australia, where it has evolved with native citrus species such as the Finger Lime (Citrus australasica). It is generally reviled for its ability to damage native and exotic citrus plants, plus its habit of spraying out a foul-smelling liquid when threatened, and the internet is overflowing with strategies for killing it. Here's an awesome image of a Bronze Orange Bug from MrsKirk72 via Pixabay.
But! We have other local bugs that aren't such a pest, and that are sometimes confused with the Bronze Orange Bug. The Growing Illawarra Natives discussion group recently had such an incident when a concerned resident shared images of an Illawarra Flame Tree (Brachychiton acerifolius) with a number of orange bugs visible on its ripening seed pods.
But on closer inspection, these bugs turned out to be a different species. They were actually Hibiscus Harlequin Bugs (Tectocoris diophthalmus), another species of sap-sucking insect that likes to hang out on plants in the mallow (Malvaceae) family. The Malvaceae family includes Hibiscus species (told you there was a link to last week's piece!) and also Brachychiton species including the Illawarra Flame Tree (B. acerifolius). They are not much of a pest, though, and rarely do major damage to the plants they're on. If you look closely at the picture you can see some orange individuals (these are adult females) with a few metallic blue patches on their back (technically their scutellum), plus some smaller red and blue numbers, which are actually all the same species. Female and male adult Hibiscus Harlequin Bugs look different (the males are more red and blue), while the earlier developmental stages (or instars) are different again. The picture below shows some bugs at an earlier instar.
But back to the Bronze Orange Bugs to finish!
If you've got them at your place or have seen them around, don't write them off as just a pest to eliminate; you can engage in a little citizen science. This species is followed by Climate Watch, an initiative by the EarthWatch Institute, the University of Melbourne and the Australian Bureau of Meteorology to understand how changes in temperature and rainfall affect seasonal behaviour of plants and animals. Its presence is tracked here.
