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What else could it be? Those white dots are the perfect camouflage for a caterpillar feeding amongst heather flowers.
Unfortunately the one thing your excellent photograph does not portray is the size of these caterpillars, in their final instar they can grow to be around 9cm (4 inches) in length.
I regularly see them in the North York Moors (though I must say I have not seen one this year yet), even so I always stop to get a closer look as they are so exotic looking.
Each warty spot has tiny irratating hairs so avoid picking them up. There are tales in the Moors of people eating these caterpillars in the 18-19th centuries during famines; however I find it hard to beleive.
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According to a document on the Cornell University website, 100g of "Emperor moth" (presumably larvae, and presumably not the same species as the British Emperor moth) contains over twice as much energy as 100g of chicken, and nearly twice as much protein, so they might have been a good choice!
These figures (and much more about eating insects) can be seen in:
which I found out about thanks to a link from Bug Girl's blog at:
Entomologist and biological recorder
Thanks for that Martin. I'll not be trying one soon though as I'm a vegetarian.
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