Silkworms are not actually worms, they are more related to the caterpillar family. They look horrible and you really need to clean them every day and feed them 1-3 times a day. As the silkworms get older they go through 3 stages where they don't eat (fasting) and then they shed their skin, often a silkworm will die because it doesn't have the strength to shed its skin, don’t get worried if your silkworms have skin dangling about them, clean them out, and it will hopefully fall of as you move it. Some of the smaller silkworms eat their shed skin, and the smaller ones are the ones that will die during each stage of fasting. The silkworms will eat Mulberry leaves, beetroot leaves, and lettuce leaves. They grow BIGGER and BIGGER and BIGGER as they eat, they will not eat much at the beginning but that does not mean that you should not clean them every single day. .
If you are keeping silkworms, or are thinking about keeping silkworms, make sure you never squash them and to never let bugs of any sort into your box. You can lose loads of them to bugs which kill your little Silkworms. That way we have lost about 1/4 to 1/3 of our silkworms to little green bugs and not cleaning them enough, but ants can kill them as can spiders. I suggest you keep about 50 we accidentally got 800 and are now down to 0, they are very hard work and look disgusting. Unless you have mulberry trees in your garden it can be very hard to get enough leaves, we have 2 in our back garden, and mulberry trees are very common round here.
They are supposed to start spinning in about a month to 6 weeks. but they will not all hatch at the same time, so if some of them are slow to spin, don't worry they just hatched later. Make sure you do not cramp them, none of ours spun as they were to crowded at first.
Before they spin they should do a wet messy poop which is rather disgusting, and really needs cleaning up instantly. I did separate mine into two sections, the ones which were going to hopefully spin soon, and the ones that should need to wait a while.
If you have an olive tree in you garden the sticks of those are very good for silkworms to spin on, but if not don't worry. you can use empty egg carton boxes, cut up toilet rolls, or cut up aluminium foil rolls, of those from cling film, feel free to try out new things for them to spin on, and if you find any other good ones please email me because I would be like to know.
Unfortunately our silkworms never span, and our local silkworm expert said that they were too crowded at first, but he was suprised that none of them spun.
For more information and some pictures of silkworms go to Kayton's Silkworm's page