Bob Gosford’s Bug of the Week: jewel bugs in the front yard

Outside the front door of my flat are two Witchetty Bushes Acacia kempeana and over the past months of this exceptional season in central Australia (we went within 12mm of a recorded rainfall record last year) I’ve spent more than a few hours peering into their foliage looking for all manner of bugs, spiders, caterpillars and all manner of other things that spend their lives in or on these two small bushes.

Every evening a spider joins me to share the sunset while I have a quiet beer. I’ll be resting and taking in the evening sky but she will be well busy setting the night’s web, unperturbed by my presence half a metre away. Once set a few small insects quickly fall prey to her sticky trap and she scuttles across to wrap them up tight, saved like fast food for later.

A few weeks ago I noticed a cluster of these bright red and green Jewel bugs on one of the branches of the Witchetty bush and over the past month or so I’ve seen several sets of eggs laid, the tiny bugs emerge and then grow through several moultings before spreading around the yard and beyond. I’ve enjoyed poking around from time to time documenting their life-cycle and the changes as they make their way to adulthood.

Jewel bugs are what are know as “true bugs” members of the Family Scutelleridae of which there are 26 species in Australia. Most are plant-sap feeders – though there are some rather gory exceptions.

I don’t know the species name of these jewel bugs from my front yard – and if you do please let me know.

Jewel bugs are closely related to stink bugs, they may also produce an offensive odour when disturbed. Particularly in young bugs, clustering behaviour is an advantage to survival. Each bug has strong smelling scent glands and when the scent is emitted by one it triggers others in the cluster, multiplying the offensive odour. Predators avoid bad-smelling, bad-tasting prey until they themselves evolve to deal with the smell, the taste and the toxins.

Jewel bugs go through several nymph stages – as you can see from these pictures. In the photo of juveniles just emerged from their colony of egg casings above when they first emerge they have a very distinctive red and black colour pattern, which later, as is apparent from the photo below, changes to a very different pattern in a beautiful iridescent green and bright orange, set off by the electric blue highlights along their shield casings and legs.

There are something like 6,000 known species of bugs in Australia and they come in a huge variety of shapes, sizes and colours. Despite the distinct differences between the bugs in these photos they are – at least I believe they are – all of the same species – the different colour combinations representing different nymph and moult stages.

If you want to know more about the world of insects and little critters like the Jewel bugs I recommend A Field Guide to Insects in Australia by Paul Zborowski and Ross Storey, published by New Holland. You can also learn more about the Scutelleridae and jewel bugs at a couple of very interesting websites, including the Order Hemiptera at Life Unseen and the Brisbane Insects and Spiders homepage and Scutelleridae pages.