Lifecycle of a silkworm

The best way to learn science is to get close to nature and observe the surroundings. Nature has immense number of secrets and wonders which can intrigue kids as well as adults. Metamorphosis is one such amazing natural phenomenon.

This spring my preschooler's teacher got some hatched silkworms from the RAFT organization so she could have her students observe their lifecycle. She initially put them them in a shoe box
(as they were tiny) with plenty of mulberry leaves. The mulberry leaves is their preferred food, however they can also eat spinach or lettuce leaves. These worms were tiny light green and rusty.

The pictures below are of the silkworm, two weeks after they were brought:



However due to their enormous appetite they kept feeding on the mulberry leaves and grew. She moved them to a big plastic container with lid. All of them grew at different rates, however not a single worm crawled out of the shoe box or the plastic container!



As the silkworms grew the teacher started keeping rolls made out of thick paper sheet in the plastic container. 4 - 5 weeks after they were brought to school the first one crawled in to the roll and started making a coccoon. It made the coccoon within a day!


In the following 1-2 weeks most of the silkworms had gone in to their coccoons. Some of the coccoons were yellow. It is normal since those were wild silkworms and can have their coccoons in non-white color. As people prefer white color (as it could be dyed in to any color) they started breeding silkworms that would give only white silk.


For commercial use the coccoons are put in to boiling water and treated while the moth is still inside the coccoon. The enzymes secreted by the moths to break the coccoon damages the silk and hence they are not given any chance to come out.
After about 4-5 weeks of being in the coccoon, the silkworm moths finally came out. At this stage they do not need any food, nor do they fly. They go through the reproductory phase, lay eggs and die. These eggs can be stored in the refrigerator and used in the next spring to hatch more silkworms.



The silk from the cocoons is very strong and is stretched in to a hankerchief after treating the coccoons. It is then spun in to thread.



The entire lifecycle of the silkworm
(egg -> catterpillar -> coccoon -> moth) spanned over 2.5 months and almost everyday me and my kids watched it with great excitement.