Shieldbugs are simple things, but still fascinating

I’ve always been drawn to the more obscure insects — small, insignificant specks that can only be appreciated down the microscope. Part of this is, I admit, my elitist snobbery, but it’s also a response to the easily available images of bright and showy creatures to be found everywhere. It’s a claim that there is much, much, more to entomology than the usual butterflies, moths, bumblebees and dragonflies, and that it’s all right to stare intently through the hand lens at a grey 3-mm picture-wing fly in a glass tube and enthuse about its one- or two-marked costa and its semaphore wing signals. Insects are so bewilderingly diverse and numerous, and they dominate this end of the size spectrum.

But it is still fine to be fascinated by some of the larger stuff.

So it is that I have just about finished the New Naturalist volume on shieldbugs. With only about 80 species in the British Isles and most of them easily identifiable on sight, or from a photograph, I’d rarely had cause to examine them closely until now; I’d normally just note the species names in the field notebook and move on. But shieldbugs are lovely. Why else would we give them such an elegant heroic heraldic name? Sure enough, they are glossy, chunky, often large and brightly coloured, and suitably shield-shaped. Shieldbugs have a regal and aristocratic air about them. My stylish pentatomid-design enamel lapel badge often draws comments because its obvious shield shape looks as if it could be the emblem of some noble family. It is, of course, but not necessarily in the way most people imagine.

Occasionally I’d pick one up and hold it in my cupped hands. Shieldbugs give off a slightly rancid marzipan smell produced from chemicals in the thoracic glands just above the back legs. This tastes bitter in the beak of any bird foolish enough to try and eat one, but I can’t resist sniffing my fingers to savour this evocative smell. Sometimes, however, one shunts out something a bit stronger.

In the autumn of 1992 Catrina and I took a last-minute adventurous holiday to Costa Rica. A few days in, and we had driven our small hire car to the tiny town of Quepos on the Pacific coast with a view to visiting the Parque Nacional Manuel Antonio the next day in search of tree sloths, agouti, white-faced monkeys and hummingbirds. We saw them all, but being an entomologist my lingering memory of the place (shortly after the sloth sighting) is of a loud rattling buzz as a large insect flew over my head. Without a thought, I jumped up and caught it in my bare hands. It was a huge orange shieldbug, probably one of the Edessa species so diverse there in the Neotropics. I held it gently, as I had done for many large insects, but it did not recognize my friendly behaviour and immediately exuded a copious amount of defensive chemical from its thoracic glands. Ordinarily I would have savoured the delicate almond aroma I knew from shieldbugs back home in England, but I was surprised to see my thumb completely stained a rich ochre brown. There was none of the accompanying pungent smell that I had come to associate with shieldbugs, but my skin was marked, immovably, for the next five days. It was quite unnerving to think of the chemical power from this insect, particularly as I’d always thought of plant bugs as being at the mild end of the insect danger spectrum. I’d like to be able to say that I was chastened by this episode, more circumspect in my future dealings with large tropical insects, but this was not the case; I continue my cavalier pick-it-up-and-see-what-happens attitude.

A few years later, demonstrating insects to small children at a local environmental event at the annual Nunhead Cemetery Open Day, I took great delight in getting my visitors to smell the mating pairs of the small bronze shieldbug Eysarcoris venustissimus, which many of them were bringing to the bug-identification stall. Holding them in the palm of my left hand I gave the still-conjoined shieldbug couples a rude poke with my right index finger and held them out to the noses of my audience. Sometimes I was given a screwed-up face of disgust; sometimes an amazed eyes-wide-open recognition from those who knew what a cocktail of almonds and diesel smelled like. But mostly what I got, by the end of the day, was a memory of that Costa Rican encounter when I noticed that following the repeated prod-and-sniff performances my left palm was marked with streaks of vague brown stain that would not be washed away. The home-grown shieldbugs, smaller, less loaded with bodily secretions, nevertheless had the same ability to tan my hide, albeit in a more subdued and gentle fashion. Despite these assaults on my epidermis, I remain unafraid of shieldbugs and continue to handle them as gently as I can. Plenty of the photos in this book are of shieldbugs crawling over my hand, or held gently between finger and thumb. Thankfully my fingers have never been tested so again.

I have a small collection of shieldbugs. Despite many being large and distinctive, there are still several that require close examination under the microscope. Sadly my first collected specimen seems not to have survived — according to my original manuscript catalogue it was specimen number 130 Acanthosoma dentatum. I found it on our family holiday to Prospect Farm Caravan Park (Caravan number 90), Swanage, on 17 August 1969. My Dad probably helped me to name it; I was only eleven. It’s a common birch-feeder now called Elasmostethus interstinctus. It is no longer in my collection; nor are 180 Piezodorus lituratus, Denton, 31 August 1969, or 626 Syromastes (Coreus) marginatus, St Lawrence, Isle of Wight, 20 June 1971. I suspect they all fell to the ravages of the museum beetle, Anthrenus verbasci. This notorious pest feeds on animal fibres in carpets (it’s also called carpet beetle) and as its name suggests it is an important nuisance in museums feeding on the preserved remains of stuffed animals and birds, and pinned insect specimens. It is against this critter that well-constructed cork-and paper-lined drawers with close-fitting framed glass lids are made to house insect collections. This level of workmanship does not come cheap and before I could afford my first proper insect cabinet I used a series of four small unglazed drawers in a flimsy desk-top cabinet more likely to have been made for stationery or knick-knacks. And I paid the price.

Shieldbugs is, apparently, due out in July. Here are a few random sample pages.


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