Silkworm

SILKWORM, a name that unites those representatives of insects of the order Lepidoptera which, during the larval stage, possess well-developed silk-secreting glands and at certain periods of their life activity release silk fiber. Some silkworms, before pupation, surround themselves with a dense silk casing, a cocoon. Such silkworms are raised for industrial purposes. Silk secretion and cocoon spinning reach their highest degree of perfection in the mulberry silkworm—Bombyx mori L. (see), which is completely domesticated, does not occur in the wild state, and has been cultivated by humans for no less than 5,000 years. Some 'wild' silkworms also have local industrial significance, i.e., those less domesticated and requiring conditions closer to natural for their cultivation. Examples are the Chinese oak silkworm (Antheraea pernyi) and the Japanese oak silkworm (Antheraea yamamai). They produce silk of inferior quality and their cocoons are more difficult to process than those of the mulberry silkworm. The widespread disease pébrine causes great harm to the industrial cultivation of silkworms. This parasitic disease is expressed in all organs of the larva, pupa, or butterfly becoming filled with spores of the parasite, so-called pébrine bodies, which leads to the death of the insect. The parasite (Nosema bombycis) penetrates with food and undergoes a complex cycle of development in the host's body. The disease spreads rapidly, as the source of infection is the excrement of sick larvae, contaminated feed, etc., and is transmitted to the next generation through infected eggs. In the middle of the 19th century, the spread of pébrine threatened sericulture in a number of regions of Western Europe and Russia. At present, a number of measures to combat pébrine have been developed, the essence of which is microscopic control over the breeders and eggs (graine) followed by the ruthless rejection of infected ones. Some silkworms, which have no industrial value, are of interest to medicine due to the irritating effect that their hairy larvae have on human skin (see Larvae, Dermatitis). These include the so-called stinging larvae, for example, the larvae of the oak processionary silkworm and others.