Word of the day: Sericulture
(Who am I kidding, these words aren’t random. I pick words that relate to Lepidoptera – from the Torre-Bueno Glossary of Entomology)
Sericulture, commercial raising of silkworms, Bombyx mori, for their silk.
There are many direct and indirect ways that insects benefit our lives. Silk is one of them – that amazingly textured fabric is the product of the domesticated “silkworm”, not a worm but a caterpillar. Sericulture refers to how the caterpillars are raised and farmed for their silk.
Why do caterpillars produce silk, anyway? And how?
Caterpillars have a pair of spinnerets behind their mandibles, which are connected to silk glands. Caterpillars produce silk for a variety of reasons – safety lines, shelters, ballooning, molting mats, cocoons, decorating themselves, and probably more! If you ever see a caterpillar suspended in mid air, it is connected to the tree above from a line of silk. If you watch carefully, you might observe it rolling the silk into a little ball as it pulls itself back up. Some caterpillars will lay down silk wherever they go, so they will never drop too far from their host plant.
When caterpillars are in their first couple of instars and quite small, they may use silk for ballooning. Spiders do this too – releasing some silk fibers into the wind, they can be blown to a new locality. This is helpful if you have a hundred hungry siblings to compete with.
Shelters can be made by silking together two leaves. Molting mats are a layer of silk that a caterpillar can hook its crochets into in order to pull out of its old skin. Cocoons are an enclosure made by some moths to protect their pupa, often made of silk and hairs. And some caterpillars will try to blend in by attaching bits of plant matter to their bodies with silk.
Humans have been taking advantage of the silk production of B. mori for about 5,000 years now. Interestingly, the species no longer exists in the wild, and is perpetuated only for the silk trade and for scientific research. The silk is obtained from the cocoon, which is made of one long strand. The pupa is then discarded or eaten. Yum!