Students can spend time learning the facts about silkworms. They are the larvae of an Asian moth species that is now extinct in the wild. The cocoons that they spin are a silky and strong fiber that many manufacturers use commercially for silk. They only eat mulberry leaves. One of the reasons they make useful and interesting classroom pets and projects is because you can control their growth. They can grow up to three inches long but can be smaller the less you feed them. As domestic insects they are also unable to fly.
Students can work with their teachers to care for the silkworms and watch them grow. When you purchase silk worms or sil worm eggs, be sure to get mulberry leaves or other "silkworm food" sold by the merchant. Keep the silkworms in a warm and dry environment such as a plastic container under a heat lamp between 78 and 88 degrees Fahrenheit. If condensation forms, open the container so it dries out. Feed the worms as often as you want by grating small amounts of their food with a cheese grater so that it falls on them. They will grow in proportion to the amount of food they receive. You should feed them at least once a day to ensure their health, although they may be able to go for a week without food. Be sure that everyone's hands are clean and dry when handling the worms, their environment or food to avoid introducing bacteria.
Perhaps one of the most useful and interesting qualities about silkworms that students can observe is the life cycle. After hatching, the silkworms are in the the larval stage for about 25 to 28 days, during which they can grow to about three inches in length. During the next stage, the pupa stage, the silkworms weave silk cocoons around themselves. They stay in their cocoons for two to three weeks until they emerge as flightless moths. The moths live for about a week, a time during which they mate and lay eggs. The eggs hatch after about three weeks, or they lay dormant for about a year. Then the process starts all over again.
Aside from observing and caring for the silkworms as a group, students can do a number of other related activities. Each student can keep his own silk worm in a container on his desk and be responsible for feeding it and keeping its environment clean and dry. You can do a number of related art projects and journal entries inspired by what students are learning. For a math exercise, students can measure the silkworm's length periodically and track it on a chart. They can learn anatomy when the silkworms are large by observing the heart and arteries beneath the translucent skin. They can also watch adult females lay eggs one at a time. Learning about silk and the silk industry can be interesting as well. Students can pull loose silk from the cocoons and see a coarse silk strand without killing the pupas. To obtain a fine silk, you must kill the pupas. Put the cocoons in a 200 degree oven for 30 minutes; then place them in boiling water and let it cool. Unwind the cocoons five at a time to make a strong silk thread.