Shield bug vs caterpillar

I think of shield bugs (stink bugs) as mainly being sap suckers. So I was surprised yesterday when I saw this strikingly coloured bug sucking the living daylights out of a caterpillar of the large white butterfly.

Bronze shield bug with caterpillar
Bronze shield bug with caterpillar

The bug was very alert and not at all keen to have its photograph taken: as I snapped, it tried to drag its caterpillar prey to the underside of the leaf; then it decided to move onto the red nasturtium flower – perhaps thinking it would be better hidden.

...trying to drag the caterpillar under the leaf...
…trying to drag the caterpillar under the leaf…
...hiding on a nasturtium flower (the caterpillar is hanging down the back)
…hiding on a nasturtium flower (the caterpillar is hanging down the back)

I couldn’t find the bug in my books, but via Google and the British Bugs website, I think it is a bronze shield bug (Troilus luridus). One of only four species of predatory/carnivorous shield bugs in the UK.

The bug is still on that patch of nasturtiums today and has moved on to an even bigger caterpillar.

Another day, another - and bigger - caterpillar. And the bronzey colours are showing up better.
Another day, another – and bigger – caterpillar. And looking a bit less scarlet and a bit more bronzey.

This is a juvenile stage of the bug, but it will soon be mature and then it will have the more classical “shield” shape and will be a much duller (and bronzey) looking bug altogether.

Incidentally, most everything is at least a fortnight “late” in the garden this year: the main influx of butterflies (and hence eggs and caterpillars)  only really arrived at the start of September

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3 thoughts on “Shield bug vs caterpillar”

  1. I have a post in draft form right now on the white-margined burrower bug (Sehirus cinctus) whose nymphs look strikingly similar to your shield bug. They are not the same as Sehirus cinctus nymphs feed on seeds of mint family plants and the adults on many kinds of plants.

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