Why do silkworms raise their heads?

¿Porqué los gusanos de seda levantan la cabeza?

Behind our work as manufacturers of silk scarves and foulards, there is also the meticulous work of the small silkworms, which elaborate the cocoons that will later be used to make this soft and delicate fabric. Although the breeding of these insects is not only reserved for silk professionals, there are many children and amateurs who have different types of silkworms at home to learn about their life cycle or simply for pleasure. A common question among hobbyists starting to breed silkworms is why silkworms raise their heads or why they stay still with their heads up.

Here is the answer!

Silkworms standing still with their heads up.

“My silkworms raise their heads and stand still with their heads up,” “What’s wrong with my silkworms?”

Well, there are many reasons that can explain this behavior of silkworms. Normally, when silkworms raise their heads, it is because they are either going through one of their phases or they are preparing to molt.

When the worms are preparing for the fourth age, they adopt this posture in a sleep phase that can last from 24 to 30 hours, which is done before molting. If your silkworms raise their heads and remain still, do not touch them and keep them out of the sun. After molting, and with a new body and a larger mouth, the worms eat a lot again in order to shorten their cycle.

On the other hand, you should keep an eye on worms that engage in this behavior because it can also be a symptom of certain diseases, many of which are deadly. In fact, some experts may recommend the removal of worms that are not in this stage from the whole as a precaution. Thus, in case of contagious disease, we will prevent the rest of the worms from becoming infected.

Why do silkworms die?

In line with the above, if you have silkworms and you notice that some of them die, you may be interested in knowing why to prevent the rest of them from dying. There are several reasons, the most common are:

  • Accidentally bitten. It is common for silkworms to eat very close to each other. This can cause them to accidentally receive a bite that was intended for the leaf. When this happens, the worms move in another direction quickly, leaving behind them a trail of yellowish blood. Usually nothing happens to them and they stop bleeding soon, but if the bite is too big, they may die.
  • Poisoning. When a worm has been poisoned, it becomes U-shaped as it writhes. This may occur because the mulberry leaves we have fed it had been fumigated. If we detect this problem we should remove all the leaves and take them from another place.
  • Flaccidity. Another common death of silkworms is caused by this disease. It usually occurs after the fourth molt. Worms suffering from it will be apparently healthy but will stop eating at any time, and their skin and body will become increasingly soft, until the skin breaks and they secrete a dark, foul-smelling liquid. Sometimes the larva of the worm will even cocoon, but it ends up dying as a chrysalis and the silk will be stained with this liquid.
  • Pebrina. This disease is caused by germs of the protozoan Nosema Bombycis. Its main symptom is a characteristic retardation of the worm’s development, loss of appetite and difficulties in making the chrysalis.
  • Muscardine. This disease is spread by the fungus Botrytis bassiana and is highly deadly. First the worms become soft, then they change to a very characteristic pink color, become hard and become petrified, as if they were covered with plaster. Although the disease is not inherited, it is easily transmitted.


Interested in learning more about these fascinating animals? Here we tell you how is made the silk we use in our silk scarves.

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