I headed to the garden with my digital camera and a 90 mm 1:1 macro lens to snap what insects I could find while it was sunny. In the end, I finally got around to pruning our wisteria, cutting back the grapevines and the bladder senna plants and the overhanging bramble from our rearward neighbour.
Two hours later, I had no insect photos until I spotted a shieldbug on a leaf in the leaf litter. Picked up on and let him run around our old teak garden table. I'd plucked a few grapes from the vines so plonked one of those in front of him for his close-ups. Needless to say, he didn't sit still for long and with the short depth of field you get with a macro lens like this it was hard to get a sharp shot on his eyes. Of course, you can use focus stacking to get a greater depth of field effect but that's hard with a moving subject like a living insect.
I couldn't find an exact match for this species and settled on it being a Birch Shieldbug. However, a more expert eye than mine pointed out that it was a Gorse Shieldbug (Piezodorus lituratus). It is "similar to the Birch but more robust and has a yellow edge to its connexivum. It's in its late summer/autumn colouration, earlier in the season they are more green, apparently.
P. lituratus is a member of the Pentatomidae, a family of insects belonging to the order Hemiptera. As I mentioned, they're commonly called shieldbugs or stink bugs. Pentatomidae is from the Greek pente meaning five and tomos meaning section and refers to the five segments of the insects' antennae.
That piezo prefix in its scientific binomial is intriguing. Piezo comes from the Greek roots (e)pi and sed together meaning to sit upon and so piezo means "pressure". As most readers will presumably known piezoelectric materials generate an electric current when you squeeze them (i.e. apply pressure) and conversely, apply an electric current and such materials change shape. So, "Piezodorus" - squeeze the bug and it produces an awful smell, not sure whether it changes shape if you expose it to an odour, presumably not. The etymology of the scientific name is obvious really, when you think about it, given that the shieldbug's alternative common name is the "stink bug"! There are lots of animals with "lituratus" as the second part of their scientific binomial. Is it related to "daubed" or "erased"? Perhaps a classics-trained reader could help out on that point.
The insects secrete an unpleasant-smelling glandular substance from pores in the thorax when they are disturbed, or squeezed, perhaps by the teeth or beak of a predatory animal. The stinky concoction contains aldehydes some of which have a similar smell to natural products coriander. Incidentally, some people love the smell and taste of coriander (cilantro, Coriandrum sativum) while others are genetically predisposed to find it offensive, like eating soap. In some species of stink bug, the secretion contains cyanide compounds and has a rank smell like rotten almonds, which presumably also helps deter predators who get too close with their mouthparts. As with coriander though, some people enjoy the odour of stink bugs. Whereas in many parts of the world, these creatures are considered a crop pest, in Laos, some species are ground up with herbs and spices to make strong-tasting cheo paste, which is then further mixed with chillies and eaten.
There is but one research paper available from a PubMed search on this particular species, and it is on the subject of the genitalia of different species. It is a topic of wide general interest to stink bug specialists presumably, but perhaps not necessarily high on the agenda for materials scientists. Fortunately, a Google Scholar search while bringing up lots of reproduction and life cycle papers (presumably of interest to those wishing to preclude these insects from feasting on crops), also turned up an old (1996) paper with the intriguing title "Wettability and Contaminability of Insect Wings as a Function of Their Surface Sculptures" [DOI: 10.1111/j.1463-6395.1996.tb01265.x].
Now, that paper sounds more like something for the materials scientists. Surface structures and wettability in insects, sounds like putative biomimetic inspiration for self-cleaning materials, composites, and meta materials. The paper looked at properties of a wide range of insects and insect types, P. lituratus gets an honorable mention for its ability to self-clean its wings. "Particle removal was relatively high in this species," the paper reports.
Of course, there has been a vast amount of materials science research into natural materials that are wettable, non-wettable, nanostructured, self-cleaning etc in the time since this paper was published. Perhaps the bug with the piezo name was just one of countless species examined or maybe it was the genetic predisposition of those researchers who came after who simply didn't like the smell and couldn't work with these animals that meant it was left to its own stinky devices. No pressure.
David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase. You can see more of his macro and other photography via his website.