The Bronze Orange Bug is a member of the greater Pentatomomorpha, the stink bugs and their allies. They are true bugs and so do not undergo complete metamorphosis. The eggs hatch into nymphs that resemble the adults in overall bodyshape, just a lot smaller.
Spring in NSW is when the Bronze Orange Bug thrive the most. And the Bronze Orange Bug is not named for its Orange middle instars, it is because they are ravenous pests of oranges and other citrus fruit. So when I went to look at my parent's lemon tree in their backyard, I found it absolutely swarmed with Bronze Orange Bugs.
Since it is breeding season for these bugs, luckily for me, I got to see the insect's entire lifecycle coexisting on the tree. Unluckily, this does mean the majority of those lemons are doomed.
Although not true stink bugs, the Bronze Orange Bug does still produce a foul smelling chemical when under attack. Like other true hemipteran bugs, they have sucking mouth parts, used to suck sap out of the citrus tree, causing flowers to fail and fruit to fall off the tree before ripening.
The youngest growth stage or instar are green and camouflage well against the tree's leaves. The later instars are yellow to orange in colour. This makes them a lot more visible, to warn predators against their chemical defenses. The adult stage grows a duller bronze-black, now more well suited to camouflage against the trunk of the tree. And if they are spotted against the fruit, the adults are more well armoured, and still capable of chemical defenses. Why they do not keep their bright orange is beyond me.
Chemical pesticides have mixed success against these pungent bugs, as they produce foul chemicals themselves. General purpose pesticides can work, but they will kill all other insects in your garden too.
Best success is physically removing the insects, and this is easier than you'd think. Stink bugs are relatively placid (likely due to their defenses), so sticking a vacuum cleaner into your citrus trees will cause most of them to sit still while they are sucked up.
