Spinnerets and Making of Cocoons

Most of our clothes, bags, valets, parachutes, tents, shoes, just to mention a few, are made of synthetic fiber. A variety of synthetic fibers are manufactured in the fiber industry.

The synthetic fiber is basically a plastic polymer which is one of petroleum byproducts. Huge machines are designed to produce fibers of varied thickness. The machines have devices with hundreds of pores. Molten plastic polymer material is forced out through these pores. Streams of such viscous material are then passed through cool air or liquid. The material gets solidified as fibers.

The same process is used in the making of cotton candy!

The special mechanical devices which perform this air stream liquid to fiber making are called Spinnerets.

In the living world spinnerets have evolved millions of years ago, they are the silk spinning organs in the insects and spiders.

The caterpillar of moths and butterflies has the spinneret located on the lower lip (labium) of the mouth. It is a tubular structure connected to the spinning apparatus or the silk glands. The silk glands are modified salivary glands. The caterpillar draws silk from the spinneret. The silk dries on exposure to air. Caterpillars make cocoons with silk.

In Colorado, Tent caterpillars (Malacosoma species) do not build cocoons. They construct silk tents instead. Inside the tents, they live, grow and pupate.

The tent caterpillars are known by their frantic head movements, back and forth. Silk extrudes from spinneret connected to a pair of long cylindrical silk glands that extend the entire length of their body.

Fine silk threads are strung in-between twigs and branches collectively by a number of caterpillars. A silk mat with many chambers and passages is constructed. It is a sort of a ‘tent’ which is used by the caterpillars for their shelter and protection and hence their name.

During day time he caterpillars move out of tent, each spinning a silk thread along its path. Chemicals are released along the threads which help in communication and recognition. The caterpillar can easily retrace its path by its silk thread, back to the tent. The silk thread is also used as a life line. The caterpillar knows its silk thread by smell and can distinguish its own from the silk threads of spider webs.

The tent caterpillars are famous for their special silk tents made from their unique spinnerets by a very simple biological process. It took man years, to copy the process!