It has been a week of illness in our household, so this is a late update. As I write this morning, there is just one silkworm left munching. The rest are safely cocooned or in the process of creating cocoons. On Tuesday, there were only a few more. Mercifully, a friend at the Guild gave me a bag of mulberry leaves last week–bless her generous heart.
I can confirm that I don’t know why some cocoons are golden yellow and some are cool white. I marked their tubes as they went in during the last week, and there is no obvious relationship between the cream silkworms on the one hand and the stripy ones on the other–and cocoon colour.
Meanwhile, the garden is a riot of green vegetables and herbs running to seed (chicory, lettuce, kale, dill and parsley) and flowers. There are at least three varieties of poppy blooming, and bees rolling around gleefully in the bowl of the larger flowers. 
The pelargonium is even more glorious than last year, too and some of the iris tubers I bought at the Guild turn out to be deep purple (I thought they were all yellow)… so my thoughts are turning to more preservation dyeing. Petal collecting has commenced!
Local & Bespoke 
The cocoon color is controlled by one set of genes, and the caterpillar color is controlled by a different set of genes, so you can have them in any combination. Since your first silkworms spun yellow cocoons, that must be the dominant color. (If you start reading up on silkworm genetics, it sounds more complicated, but that’s about what it works out to.)
“Purebred” silkworms can exist, where they all look alike and produce matching cocoons, but that wouldn’t be so much fun 🙂
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Thanks, Nat! I had no idea. And you’re right… everything the same wouldn’t be as much fun 🙂
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