I am raising a Thai strain of silkworms.  This spring, I had one good-sized group, and they all made moderately sized cocoons – except for one, which turned out tiny.  The summer group, I will admit, got a little bit neglected; I moved during the middle of their cycle, and  so they sometimes got not enough food, or old leaves because I couldn’t find the new ones near my new house… you get the idea.  Poor little red-headed step-child worms.

So – some of them decided that life was tough, and they would cocoon early.  They spun up in the fourth instar, making TINY but perfectly-shaped cocoons.  My friend Eika explained that these are called trimoulters, and they are typically caused by feeding over-matured leaves.


Now – these are a naturally small strain.  Chihuahua puppies are never going to grow up to be German shepherds – but the trimoulters are *freakishly* small.  Here’s a comparison of normal Thai cocoons, hybrid Chinese cocoons, and the trimoulters.


and here’s a comparison of the normal (smallish) Thai pupa, and the trimoulter pupa


And, in a move that should surprise no-one, they hatch out as freakishly small moths.  They’re SO CUTE.  Like pinchums-widdle-cheekses cute.


Despite being tiny, they are breeding vigorously.  I’m curious to see what will come of it – and whether the eggs will be visible.

0 replies
  1. omenode
    omenode says:

    I don’t comment much, but I love your dedication to your art. Thanks for sharing these photo’s. The tiny cocoon is similar to my mid season leaf, as in it has a different and unique quality in the way it dries to mature leaves.
    Do the tiny trimoulters produce a different kind or quality thread / silk?

  2. admin
    admin says:


    I honestly don’t know about the quality of the silk – it seems natural that it would be significantly finer, but I haven’t had enough of them to experiment with yet. Maybe if I get a bunch with the next batch I’ll give it a try. So many of the techniques rely on specific characteristics of the cocoons – I don’t know if these would even have enough weight to unwind properly.

  3. tilia_tomentosa
    tilia_tomentosa says:

    LOL the tiny creatures look vigorous enough, and just as keen on mating as any other Bombyx moths. They have very good wings!

    *takes a container of her own moths and tries to compare sizes*

    At least I can see that the cocoon is smaller than my smallest cocoon (one of my silkworms spun up too early into its 5th instar; I bet I’m going to get a tiny male moth.)

    I’m wondering if your micro-moths are going to live shorter than the others – they have less food supply to be sure.

  4. admin
    admin says:

    It seems like they would have less reserve of fat, but also like they would *need* less, with their smaller size.

    My friend Michele who had some similar tiny cocoons (from the same strain) said that hers had normal-looking full-size eggs, just fewer of them.

  5. tilia_tomentosa
    tilia_tomentosa says:

    I had a tiny male last year that lived only 3 days instead of the usual 5 to 7 for my strain. But he was very vigorous while he lived. Mated and bred all right.

    Well, you’ll see the eggs pretty soon. 🙂

  6. admin
    admin says:

    Re: Food

    Yup, they eat the same mulberry. In their native land, they might eat a different one – some of the southeast Asian mulberries have little leaves – but if they’re raised commercially, they probably plant some variety of M. alba.

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