section_path: Animals/Invertebrates
section_name: Invertebrates
paragraph_text: Invertebrates
  
  Two insects, the silkworm and the western honey bee, have been domesticated for over 5,000 years, often for commercial use. The silkworm is raised for the silk threads wound around its pupal cocoon; the western honey bee, for honey, and, from the 20th century, for pollination of crops.
  
  Several other invertebrates have been domesticated, both terrestrial and aquatic, including some such as Drosophila melanogaster fruit flies and the freshwater cnidarian Hydra for research into genetics and physiology. Few have a long history of domestication. Most are used for food or other products such as shellac and cochineal. The phyla involved are Cnidaria, Platyhelminthes (for biological pest control), Annelida, Mollusca, Arthropoda (marine crustaceans as well as insects and spiders), and Echinodermata. While many marine mollusks are used for food, only a few have been domesticated, including squid, cuttlefish and octopus, all used in research on behaviour and neurology. Terrestrial snails in the genera Helix are raised for food. Several parasitic or parasitoidal insects, including the fly Eucelatoria, the beetle Chrysolina, and the wasp Aphytis are raised for biological control. Conscious or unconscious artificial selection has many effects on species under domestication; variability can readily be lost by inbreeding, selection against undesired traits, or genetic drift, while in Drosophila, variability in eclosion time (when adults emerge) has increased.