Growing Your Own Gut
By Jim Blais

The historic aspects of dressing Atlantic Salmon flies can take a fly tyer down a number of interesting paths. Sourcing quality materials; whether that is feathers, silks, threads, furs or hooks can be as much of an adventure as mounting a set of wings. One of my more notable journeys down this material sourcing path was attempting to grow my own gut for the ?gut loop? utilized on classic blind-eye hooks.

I have been brought up in the age where you typically purchase anything you need at a local store, fly shop or now even over the Internet. It thus intrigued me, when listening to Marvin Nolte in a workshop, that he talked about once raising his own silk worms for the gut I normally purchased and took out of a cellophane package. I knew, (or had been told), that true gut was actually a stretched out silk gland of a silkworm moth, (Bombyx mori), but I could not quite visualize getting this 10-18? fish-line type material out of a caterpillar! So, like many things that spark one?s interest, I set off to see what it would take to grow my own herd of silk worms!

Internet search engines were not as easy to use as they are today so my pre-Google searches for information on how to do this brought me our local library. The July 1951 issue of the National Geographic Magazine had an entire article on Spain?s Silkworm Gut industry, (pages 100-108). The article provided a basic description of the process and provided a number of great pictures so typical of National Geographic. Even with all of the information that you can source today on silk worms over the internet, this old Geographic article is worth checking-out. Click on NATIONAL GEOGRAPHIC SILK GUT ARTICLE to see it.

There are probably different sources for purchasing silk worm eggs but I brought mine over the Internet from MULBERRY FARMS They provide a small quantity (~200) conveniently glued to a petri dish and I kept only 25-50 of them to hatch. I also purchased a Styrofoam incubator and their ?silkworm chow?. Chow is a powder made up of mulberry leaves that you mix with water, cook like meat loaf and store in a refrigerator. It is an easier alternative than having fresh Mulberry tree leaves. (Mulberry leaves are the only thing a silk worm will eat.) At the time, that was a big plus for me because I was in early months of a Michigan winter!

Sue Kayton has a web site SILKWORMS that provides some great information on the specifics of raising silk worms. It is a pretty simple process so I will simply leave you with that link to reference along with the above mentioned National Geographic article.

Click on the thumbnails to enlarge the pictures:



The silkworms hatch to from pin-prick size grey-black egg and grow to a ~3-inch long caterpillar in roughly one month, (see picture1). When the time came that I found two caterpillars had already begun to spin themselves a cocoon, I figured that was my clear indication that it was time to harvest the remaining caterpillars. (You want to harvest them just prior to their using up their silk gland for spinning a cocoon.)

A pickling bath of vinegar and salt is prepared. I kept adding salt until it would no longer dissolve as I mixed the vinegar and salt solution. The Geographic article quotes a woman?s recipe: ?Add salt to vinegar until an egg will float three-quarters submerged.? (I did not want to bother with the egg!) The caterpillars were then placed in the lethal bath for approximately twelve (12) hours. (I was told that soaking them for less than 12 hours will provide a thinner diameter gut strand and a thicker diameter strand if soaked for more than 12 hours.)

To harvest the gut, simply cut the caterpillars open and isolate the silk glands which are very easy to recognize, (see picture 2). Take one of the glands with both hands. Simply pull it, with an even and consistent force and it will pull out, (something like taffy) to a length of 10-18 inches. (You will probably screw-up the first one or two but you will quickly get the hang of it.) Do the same with all of the remaining silk glands. When you are done, there is a skin or ?carne? remaining on the strands. Wash them in warm soapy water and you can scrape this carne off easily with your fingernails. The end results are gin-clear piece of gut. You then just lay them or stretch them out to dry.

Click on the thumbnails to enlarge the pictures:



After drying, coil three of them up, put them in a cellophane bag with a $20.00 price tag on it and you probably know what to do with them from there!