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RAISING AND SPINNING SILK FROM CECROPIA MOTHS

The Cecropia Moth has one life cycle per year:

• Cocoon formed mid- to late- August
  
• Moth emerges from cocoon mid-to late- June
  
• Adults live only a few days in the wild, long enough
  to mate and for the female to lay fertilized eggs
  
• Eggs hatch in about 2 weeks (early- to mid- July)
  
• Caterpillars eat and grow until mid- to late- August
  
  

Butterflies and Moths have a proboscis (like a curled-up straw) for drinking nectar, and sometimes sap from trees, juice from rotting fruit, mineral deposits from the edge of puddles and minerals from dung. The Cecropia Moth (and other species in the Giant Silkworm family) have evolved to have no mouthparts or digestive system. This is why the adult moth lives only a few days, as it lives only off its stored energy.

The Cecropia Moth caterpillar gets to be 4 to 5 inches long. When it first hatches, it is a teeny black caterpillar with black spines. After the first instar (shedding of skin) it is orange with black spines. After a later instar it is green with funny bumps (called tubercles) on it. There are blue ovals on the side of the caterpillar. These are called spiracles and are for breathing air.

It takes the caterpillar a few days to make the cocoons from silk that is spins. It takes about 4,000 to 5,000 feet of silk to make the cocoon.

Cecropia moth adults are the largest moths in North America. The wingspan of this moth is up to SIX INCHES! It is a beautifully patterned moth, with reddish-brown, black, and white wings, and a furry body with reddish-brown and white bands.

Food Plants and Raising Caterpillars in Captivity

These caterpillars usually eat wild cherry tree leaves, but also eat fruit tree leaves like peach and pear and blueberry. They will eat Norway maple and lilac leaves as well. If you are raising the caterpillars, it's best to use wild cherry or Norway maple branches. Of the two, the caterpillars seem to grow best on wild cherry. Both plants take about a week to wilt when the branches are placed in water - other food plants will wilt in just a couple of days. You can also see the caterpillars better on branches rather than buried under leaves.

If you do raise your caterpillars on branches, please insert the branch through plastic wrap or some such barrier. Mash the cut end (the branches stay fresher longer) before inserting into the water. Tie a rubber band around the bottle opening. The caterpillars don't know better than to walk down the branch into the water and may drown.

It's best not to try to pull the caterpillars off a leaf to transfer it to a new one, as the legs may tear. The easiest, quickest way cut off the leaf or portion on which the caterpillar rests, and to pin the old leaf onto the new leaf (without pinning the caterpillar in the process!)

The caterpillars will generally not wander from the branches unless the leaves have dried out or have all been eaten. They will wander when they are ready to pupate. Perhaps separating from each other makes it less likely that predators will find all of them.

Late in August most of the caterpillars are full-grown, and start to make the cocoon. Some start in early August, and some wait until November!

In the wild, the cocoons just stay on the trees all winter. It's best to keep the cocoons outside, or the moths may think spring has come and emerge from their cocoons in the middle of winter. One way is in an aquarium with a screen top (so that the mice and birds can't get to them), in a sheltered place (so the aquarium won't get snow and rain in it). Another type of container will hold the generation of Cecropia moths, eggs, caterpillars, and cocoons. This lightweight cylindrical container is made of 4 embroidery hoops, fine green nylon mesh (from a fabric store), and florists' wire. The mesh is placed between two hoops, top and bottom. The florist wire binds the hoops together and supports the height of the cage. Green mesh is easy to see through, and the moths don't shear their wings as much on nylon as on window screen. This container makes transportation easy. It may be placed inside paper bags to help the moths settle down and live longer.

Mating or Releasing Moths

It will take 2-3 hours for the wings to stiffen and dry, once the moth emerges from the cocoon. Since they do not live very long, it is important to release the moth the night that it comes out.

If the moth has emerged during the night, you could release it in the shade, in a sheltered spot like the edge of the woods. It probably won't fly out when you open the box (it doesn't usually fly in the daytime), so you might have to coax it out on your finger. They seem to climb on your finger when you put it in front of them. They won't bite or anything, but they are strong, and may flap around. Until you release it, best to keep it in a shady cool spot so it doesn't flap around in the box.

If the moth emerges during the day, please release it as late in the day as possible. If you are squeamish about releasing it, could you find someone to help.

You may wish to keep track of when the moths emerge and compare it to when they made the cocoon, so keeping tags on the cocoons may help.

When your moths emerge, check out the feathery antennae. The males have much wider antennae for smelling the females; the females have skinnier ones. It is not easy unless you have seen both, so don't worry if you can't tell.

Suppose you want to raise a new brood. Cecropias live only a few days - which is enough time to fly around and find a mate. They will usually mate overnight. If you have a female, and you want to mate it with a wild male, you may tie a thread around its waist and tie the other end in the bushes where it will be hidden from birds. Female cecropia moths produce pheronomes (which we can smell as a musty odor.) These will attract males from as far as 3 miles away. Once the moths have mated, place the female in a brown paper bag that is closed. She will lay her eggs. The eggs are fertile if they do not have a brown spot in the middle. You can cut apart groups of eggs on the brown paper for distribution. Alternatively, you can keep several cocoons together. Hopefully, the moths will emerge at about the same time so that they can breed. If not, you can keep the earlier moths in the refrigerator. That will extend their lifespan.

Cecropia Cocoons

Cecropia moths are giant silkworm moths and produce silk in their cocoons as the Bombyx mori (mulberry-eating silkworms) do. The cocoon can be recognized in the wild because it is made along a twig. Before turning into a pupa, the caterpillar chews a hole on one end of the cocoon, which is where it will emerge as an adult. You might try cutting open a cocoon from which the moth has already emerged. Cut through the open end with a pointed scissors. You will find two layers of the cocoon. Inside the cocoon are the last shed skin of the caterpillar (before it became a pupa) and the outside layer of the pupa. This outside layer shows the head, eyes, undeveloped wings, thorax, and abdomen of the forming moth. It also shows the antennae, which will tell you whether this was a male of female.

Making Silk

You may decide to try making silk with your cocoons. The cocoons are pretty stiff to start with because of the sericin that binds the silk together. Sericin: nitrogenous, gelatinous material found on the surface of silk. After the moth has emerged, you can boil the cocoons in water with washing soda added (you can use Arm and Hammer detergent). The water will take on the color of the cocoons as the sericin dissolves. The cocoons will soften and collapse in about 45 minutes. When the fibers separate easily, you'll know that you're ready for the next step. Incidentally, many different cocoons may be used for spinning silk; the luna moth is one such example

Tease apart the cocoon with toothpicks or skewers. Keep the cocoon wet while you are working with it. The silk becomes stiffer when it dries. If you want, you may work the silk down into individual strands. In processing Bombyx cocoons, the silk is reeled in one long strand and later spun together with other strands to make silk for weaving. (Cecropia caterpillars make about a mile of this) You may choose to store the spread-out cocoon on a rack (four skewers bound together will work) or spin the silk as is. If you wish to spin the silk by hand, you can either draw out and twist the silk into thinner or thicker threads as you wish, and wrap it around a twig or spool. Or you may use a drop spindle.

A simple, light drop spindle may be made from a twig with a hook and very little space above the hook (for proper balance) and a 4-5 inch disc from corrugated cardboard for the counterweight. (We will not go into detail about how to use a drop spindle here, but a web search will show the details). Then you have silk thread to work with. Cecropia silk is a little coarser than Bombyx fiber, and much of it retains wonderful earth tones. It can be blended with wool and dyed.

Madeleine Champagne and Matt Schoeffler wrote this article, with MUCH input from Helga Burre.