I have been visiting the Purple Empire site and blog for a little while now and hoped these photos would be of interest.
The first is, I believe, of an old acquaintance of Matthew Oates, found at Clacket Lane service station early this May. Interestingly, although the shadow of the larva was clearly visible from below, the larva itself was in the usual "praying" posture which I understood was adopted to avoid the casting of visible shadows! Obviously not in this case. Perhaps the posture is adopted so that the shadow cast resembles that of an unfurling sallow leaf - I have shown a typical example casting a vaguely caterpillar-like shadow on the second photo. I could find leaves like this commonly on the Somerset Levels in late May and early June, though sadly none that replicated the horns that distinguish His Majesty.