Tortoise bug

I looked with disfavour at the raft of tedious stuff that needed doing at home this morning, contemplated the fact that from Wednesday onwards I'm likely to be running flat-out for five straight days, eyed the weather (bright, sunny and warm), checked the forecast (deteriorating).... and decided that nothing in my life was currently more urgent than a few hours of invertebrate therapy. So I zoomed off to Trench Wood, where I discovered to my surprise and annoyance that I wasn't the only person in Worcestershire to have had this idea, and I had to queue for a space in the car park.

Luckily there's nothing more calculated to restore my good humour than the sight of an invert I've never photographed before, and I hadn't even made it up to the top of the entrance path when I spotted this tortoise bug. I knew they were present at Trench because someone tagged me in a photo of a nymph last week, but this adult was the first I'd ever seen. It was on a messy and unphotogenic agglomeration of creeping thistle and bent and broken grass stalks, but when I offered this lone stalk it stepped cooperatively aboard, and sat impassively while I took my photos.

We have two species in this country that are commonly referred to as tortoise bugs, and separating them definitively requires genital examination, but there are some lines I think it's better not to cross. Working on the rule that common things are commonest, and the fact that this specimen has fairly distinct 'shoulders' to the pronotum and a slight dish in the front edge of the face, it's almost certainly Eurygaster testudinaria. The other species, Eurygaster maura, is slightly smaller, has a more smoothly rounded profile, and so far as I know has only ever been found quite a long way south of the Shire.

Wikipedia lists forty six species of shieldbug as having been recorded in the UK, but only five of them fall within the family called the Scutelleridae. The distinctive feature of members of this family is that they don't have an obvious scutellum, or shield, and for this reason they're sometimes mistaken for beetles. If you view this photo full-screen though, you should be able to see that there is a scutellum, but it's enlarged to form a single plate that covers the abdomen and wings. Because of this the Scutelleridae are sometimes called shield-backed bugs. In many places they're also called jewel bugs or metallic shieldbugs, because this family contains some of the gaudiest shieldbugs in the world, but our UK species are all understated to the point of drabness. Having said which, there is quite a lot of variation in the colouring and markings of Eurygaster testudinaria, as you can see if you check out the British Bugs page, but mine was definitely at the subtle end of the spectrum.