Animal Diversity Web

Geographic Range

Bombyx mori originally existed in the wild throughout Asia. Though they are believed to no longer exist in the wild, they are in the care of the silk industry in Asia and Australia (Savela 1998).

• Biogeographic Regions
• oriental
  • native
• australian
  • native

Habitat

Although B. mori is native to China, it does not live in the wild any longer because of sericulture (Encarta 1998).

• Terrestrial Biomes
• forest

Physical Description

The larvae of B. mori are caterpillars that are about 4 cm long, including their horned tail. They are buff-colored with brown thoracic markings. The adults are moths with a 4 cm wingspan. They are also buff-colored, but have thin brown lines on their whole bodies (Herbison-Evans 1997). Another silkworm, Bombyx mandarina, appears to be a wild race of B. mori (Savela 1998).

• Other Physical Features
• ectothermic
• bilateral symmetry

Reproduction

Bombyx mori are holometabolous and reproduce sexually. The female adult dies upon depositing her eggs (Encarta 1998). These eggs weigh in at a miniscule 1/30,000 of an ounce each (Knowledge Adventure 1997). After 10 days, the eggs hatch and hungry larvae emerge. They are segmented and have body hair. The larvae eat and grow for approximately 6 weeks, and then they begin the next stage of their lives. Bombyx mori produce a fluid in their silk glands that is forces through spinnerets on their mouths. This fluid hardens in the air to produce the silk thread that they will wrap around themselves to form their cocoons. Bombyx mori spend 2 weeks as pupae in the safety of their cocoons before emerging as adults (Encarta 1998). Inside the cocoon, much of their bodies die by an attack of their own digestive juices. This process, histolysis, clears away the old parts to make way for the new ones that will develop in this pupal state. After this process is completed, the adults break free from the cocoon in order to begin the cycle again. The adults are winged and have traded body hair for scales. They are dramatically different form their larval stage (Lepidoptera Part 2 1997).

Behavior

Bombyx mori are social creatures which can locomote. Because of their role in sericulture, the adults of the species can no longer fly (Herbison-Evans 1997). B. mori have compound eyes and can hear both each other and other animals (Lepidoptera Part 2 1997). On the tip of the abdomen of female B. mori, there is a pheromone-secreting gland crucial to the species' mating ritual. When females secrete their pheromones, males begin to do a "flutter dance." This helps males and females find each other. It is suggested that if a female's gland were to at once release all the pheromones, one trillion males would be attracted to her in an instant (Pines 1997). Also important in the mating ritual are the males' larger, more plumed bodies, which entice the females (Lepidoptera Part 2 1997).

Food Habits

Bombyx mori are herbivores. They feed specifically on white mulberry leaves, but also eat Osage oranges and lettuce. They do most of their eating in the larval stage (Encarta 1998). The larvae have mandibles for feeding, while the adults have sucking mouth parts (Lepidoptera Part 2 1997). Because they have been cultivated for so long for sericulture (the silk industry), B. mori have lost an adaptation helpful to feeding in the wild. The larvae can no longer hang on plants at gravity-defying angles, and must be fed by humans (Herbison-Evans 1997).

Economic Importance for Humans: Positive

In 1989, 74 thousand tons of silk were produced (Lepidoptera Part 2 1997). Even with each cocoon yeilding one half mile of fibers, that is an astounding amount of silk (The Animal World 1990). Bombyx mori is an incredibly important species to humans because we rely on their silk for our textile and clothing industries. For many years, China had a monopoly on the benifits of this industrious animal. In fact, Bombyx mori are one of the few animals that carried the death penalty as a punishment for smuggling them out of their native country (Lepidoptera Part 2 1997).

Bombyx mori are quite important animals in the science world as well. They are used in Australia for educational purposes in schools (Herbison-Evans 1997). Scientists in the field of sericulture are working on mapping their genes in hopes of improving the quality of the world's silk and expanding our knowledge of genetics in general. Bombyx mori were the animals in which pheromones were first discovered and named (Pines 1997).

Conservation Status

Bombyx mori is currently not an endangered or threatened species; however, many animal rights activist groups object to their use in sericulture. One of the main things the activists are offended by is the silk industry's practice of boiling cocoons with living pupae inside in order to get the silk (envirolink 1997).

• IUCN Red List [Link]

  Not Evaluated

Other Comments

In homeopathic medicine, the sun-dried bodies of B. mori are believed to stop convulsions due to epilepsy or fever, cure rubella and itching, help the spleen and treat wind/heat stroke (Monograph 1997).

The silk gland of B. mori is 1/4 the total body weight.

The first person to breed B. mori for silk was the Chinese empress, Si Ling-chi. Only the empress and her female attendants knew how to get the silk, and the punishment for revealing the secret was death (Knowledge Adventure 1997).

Contributors

Katie Clay (author), University of Michigan-Ann Arbor.

References

1990. The Animal World. ed. Ann Kramer. World Book, Inc., Chicago.

1998. Encarta Concise Encyclopedia Articles. http://encarta.msn.com

1997. http://envirolink.ag/arrs/essays/silkworms.html

1997. Herbison-Evans, Don. Lepidoptera Larvae of Australial. http://linus.socs.uls.edu.au

1997. Knowledge Adventure. http://www.adventure.com/encyclopedia/bug/rfisilkw.html

1997. Lepidoptera Part 2. http://www.ex.ac.uk/gjloamel/lepidop2.html

1997. Monograph. http://www.healthlink.com.au

1997. Pines, Maya. Pheromones and Mammals. http://www.hhmi.org/senses/d/d230html

1998. Savela, Markku. http://www.funet.fi/pub/sci/bio/life