Which caterpillar eats flag iris?

September 11 2021 was when I last published an update here. I can't even begin to tell you what's happened to prevent me finding time to publish again until now; therefore, I won't!

Let me instead attempt to transport you back even further. To a month prior to that last update to be precise. In August of last year, whilst attempting to clean out the garden pond (I call it a pond, in the manner of a grand 'Hyacinth Bucket' proclamation. But actually it's no more than a large, plastic, saucer-shaped container), I spotted something tiny clinging to the flag iris that's growing surprisingly well in its confinement. 

I had to put the macro lens on it to even see what it was. Or as it transpired to see, what they were, there were several. Here's the very first image I captured...

This photo was taken on August 8th (alright it wasn't exactly a month before my last update, but close enough) and revealed that it was a larva of some description. But at this point I did not recognise it and could find no clues by researching the food-plant.

All I could say with any confidence at this stage, was that this was a moth larva.

Here's a photo from two days later...

It seems to have moulted and lost those dark hoops around the abdomen.

By August 16 some of the larvae had changed again, and now looked a little greener, with a stripe along the top of the abdomen...

Others seemed to develop a lateral white stripe...

At last I was beginning to think I might at least know which moth family these were. This must be one of the Ermine moths: quite possibly the most commonly spotted of all the hairy caterpillars too!

This image (above) was taken on September 2nd. It's now looking much more familiar with me.

One month after I first spotted these intriguing caterpillars, they had moulted for the final time and looked like this...

It was obvious to me now that these were indeed Ermine moths in waiting: Spilosoma luteumis is in fact the Buff Ermine moth.

The Buff Ermine is found in a wide range of habitats, including gardens. They are noted for feeding on low-growing herbaceous plants, including dandelion, dock and nettle, honeysuckle and hop. But the use of flag iris was confusing me, having not ever seen reference of that particular plant being used.

They will now over-winter in a cocoon amongst leaf-litter. The adult moths should emerge in early May.

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I've saved the video until last, as it's kinda lengthy. It is fascinating however. I have been unable to decide if the constant movement from within the larva is just natural digestion occurring, or anything more sinister. This individual did make it to full term okay, so hopefully it's the former...

                    You'll need to view this online; not in an emailed version of the blog...